【トラブルシューティング】Microsoft Teams のチャットで他ユーザーにメンション（@mention）ができない SI（サービスインシデント）が発生【TM286629】【復旧済み】【PIR】 | トラブルシューティング（Windows）

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Microsoft 365 のサービス正常性（TM286629）にて、Microsoft Teams デスクトップクライアントのチャットで他のユーザーにメンション（@mention）が行えないことのある SI（サービスインシデント）が発生していました。

“TM286629” のサマリー

問題

Microsoft Teams デスクトップクライアントのチャットで他のユーザーにメンション（@mention）が行えない

回避策

・”@” の後にスペースを追加することで、メンション（@mention）機能が正常に動作します。
・IME（Input Method Editior）の設定を英語に変更することでも正常に動作します。

現在

・影響の受けているすべての環境に対して修正プログラムの展開を完了しました。
※ この修正により、影響を受けていたユーザーは Microsoft Teams デスクトップクライアントを最新バージョンにアップデートの上、確認を行ってください。
なお、影響を受けていた環境へのモニタリングの結果、本事象の影響が改善していることを確認しています。
・今後は同様の問題が発生しないように新機能の設定プロセスを見直すとのことです。

原因

Microsoft Teams のチャットに [返信] 機能を追加するパブリックプレビューにメンション（@mention）機能に予期せぬ影響を与える設定ミスが含まれていた。

影響範囲

日本国内でパブリックプレビューを利用している Microsoft Teams の IME（Input Method Editior）の入力言語が日本語に設定されているユーザー

Some users are unable to @mention other users within Microsoft Teams chats when using the desktop client – TM286629

サービス：Microsoft Teams

状態：Post-incident report published

ユーザーへの影響：Users are unable to @mention other users within Microsoft Teams chats when using the desktop client.

Microsoft 365 のサービス正常性（TM286629）にて、Microsoft Teams デスクトップクライアントのチャットで他のユーザーにメンション（@mention）が行えないことがある SI（サービスインシデント）が発生していることを発表してます。

この問題の影響を受けているユーザーは、回避策として “@” の後にスペースを追加することで、メンション（@mention）機能が正常に動作します。

また、IME（Input Method Editior）の設定を英語に変更することで回避することもできます。

現在は、この問題は改善しています。

この問題は、Microsoft Teams のチャットに [返信] 機能を追加するパブリックプレビューにメンション（@mention）機能に予期せぬ影響を与える設定ミスが含まれていたことにより発生していたとのことです。

今後は同様の問題が発生しないように新機能の設定プロセスを見直すとのこと。

※ この問題は、日本国内でパブリックプレビューを利用しており、Microsoft Teams の IME で入力言語が日本語に設定されているユーザーに影響が出ている問題になります。

Post Incident Repot（PIR）

Incident Information

Important Note

This is a preliminary Post Incident Report (PIR) that is being delivered to provide early insight into details of the issue.
The information in this PIR is preliminary and subject to change.
A final PIR will be provided within five (5) business days from full event resolution and will supersede this document upon publication.

Incident ID

TM286629

Incident Title

Some users are unable to @mention other users within Microsoft Teams chats when using the desktop client

Service(s) Impacted

Microsoft Teams

User Impact

Users’ OneDrive for Business storage limits were lower than expected.

Users are unable to @mention other users within Microsoft Teams chats if using the desktop client with Japanese IME.

Scope of Impact

This issue affected any Microsoft Teams user who has public preview features enabled and have set Japanese as the input language via IME in Teams.

Incident Start Date and Time

Thursday, September 16, 2021, at 12:00 AM UTC

Incident End Date and Time

Monday, October 18, 2021, at 11:00 PM UTC

Root Cause

A public preview feature that enabled the “reply” option in Microsoft Teams chats was released with a misconfiguration that prevented users from @mentioning other users within Teams desktop clients using the Japanese IME.

Actions Taken (All times UTC)

Thursday, September 16

・1:23 AM – We received a report of impact to the @mention feature within Microsoft Teams and support resources started to triage with the users affected.

Wednesday, September 22

・8:08 AM – We triggered a high-priority investigation after receiving additional reports of impact. All reports originated from users hosted within the Japan region.
・8:30 AM – We started analyzing network trace logs provided from impacted users.
Additionally, we received reports that not all users within an organization were affected, but the ones who were affected were constantly reproducing the issue.
・9:00 AM – We continued reviewing Fiddler network trace logs.
・9:37 AM – We gathered additional Teams client diagnostic logs to identify the errors which was causing the issue.
Additionally, we identified that if a user typed ‘@ name’ with a space between the @ and the name, then the @mention feature worked. We provided this as a workaround.
・9:40 AM – We reviewed recent changes to the service as a potential root cause.
We focused on a specific update which was deployed to 10% of users in the Japan region on September 16th.
・9:56 AM – We reviewed options to disable a feature flag, related to the recent update, as a possible mitigation strategy.
・10:07 AM – We started to use a test account to test disabling the feature flag and validate if the strategy was successful.
・10:15 AM – After further investigation, we determined that the issue would only affect users who had their system language set to Japanese.
・10:24 AM – We determined that the offending update was related to the release of a new ‘Reply’ feature, which allowed users to reply to chat conversation.
This feature was still in Public Preview.
The change had been deployed to 10% of users within the Japan region.
We discussed options to disable the ‘Reply’ feature to mitigate the impact to @mentions; however, disabling the ‘Reply’ feature would also generate customer reports for users who become accustomed to using the feature.
・10:57 AM – We confirmed that a code fix would be required to address the underlying issue without impacting either the ‘Reply’ or @mention features.
We decided to disable the ‘Reply’ feature for organizations who had reported impact to @mention functionality and give them the option to re-enable if they preferred the ‘Reply’ functionality.
We started to review options for the long-term fix; however, expected this planning stage to require several days to complete.

Saturday, September 25

・1:03 AM – We determined that the feature flight setting was stale, which caused the process to remove the feature to not work correctly.
We retriggered the feature disablement and contacted users to confirm mitigation.
As this occurred outside of Japanese business hours, we expected that we were unlikely to receive customer confirmation until the beginning of the week.

Tuesday, September 28

・1:07 AM – We received confirmation from some users that impact had been remediated for the @mention feature.
We also received additional reports of impact and began disabling the ‘Reply’ feature for these organizations in parallel with work to develop a long-term fix for allowing the ‘Reply’ feature to be reenabled without impact to the @mention feature functionality.

Thursday, September 30

・1:19 AM – Work on the Microsoft Teams client fix continued.

Friday, October 1

・1:30 AM – We continued working on the Teams client-side fix.
Due to the complex nature of the fix, we wanted to ensure there was no additional impact to the features.
We expected the development and testing process would take approximately three weeks to complete. Once finished, we would begin deployment to the affected users.
We confirmed that setting the Input Method Editor (IME) to English also mitigated impact for the @mention feature and updated our communications to include this.

Wednesday, October 6

・1:21 AM – We continued developing the fix and expected to begin deploying it to the first Microsoft internal testing environment the same week.
Per this timeframe, we anticipated deployment to affected users to complete between mid to late October.

Thursday, October 14

・1:52 AM – Initial validation testing within the internal environments was successful, and we started deploying the fix within the production environment, enabling it for 10 percent of users within the Japan region.
We continued monitoring to ensure there were no additional issues before deploying the fix to a larger user base.

Monday, October 18

・11:00 PM – The fix had been deployed to 100 percent of the affected environment.

Tuesday, October 19

・1:05 AM – We confirmed that users would need to update to the latest Microsoft Teams client version to experience remediation.
We entered a period of extended monitoring and contacted previously affected users to confirm resolution.

Thursday, October 22

・12:31 AM – We received confirmation from several users that the impact had been remediated. We declared the incident resolved.

Next Steps

Findings

Action

Completion Date

A recently introduced public preview feature, which adds the “reply” option to Microsoft Teams chats, contained a misconfiguration causing unexpected impact to @mention functionality.

We’re reviewing our new feature configuration processes to ensure similar events do not occur in the future.

November 2021

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October 26, 2021 10:30 PM – Service restored

A post-incident report has been published.

October 22, 2021 9:30 AM – Service restored

・Title : Some users are unable to @mention other users within Microsoft Teams chats when using the desktop client
・User Impact : User Impact : Users are unable to @mention other users within Microsoft Teams chats if using the desktop client with Japanese IME.
・More info : As a workaround, users were able add a space after the “@” which triggered the @mention function to work as expected.
Additionally, users were able to switch their IME (Input Method Editor) to English as this was not impacted.
・Final status : We’ve confirmed with various customers that the issue has been successfully resolved.
・Scope of impact : This issue affected any Microsoft Teams user who has public preview features enabled and have set Japanese as the input language via IME in Teams.
・Start time : Thursday, September 16, 2021, 9:00 AM (12:00 AM UTC)
・End time : Tuesday, October 19, 2021, 8:00 AM (10/18/2021, 11:00 PM UTC)
・Preliminary root cause : A recently introduced public preview feature, which adds the “reply” option to Microsoft Teams chats, contained a misconfiguration causing unexpected impact to @mention functionality.
・Next steps : – We’re reviewing our new feature configuration processes to ensure similar events do not occur in the future.
We’ll publish a post-incident report within five business days.

October 20, 2021 11:34 AM – Service restored

・Title : Some users are unable to @mention other users within Microsoft Teams chats when using the desktop client
・User Impact : User Impact : Users are unable to @mention other users within Microsoft Teams chats if using the desktop client with Japanese IME.
・More info : As a workaround, users can add a space after the “@” which should trigger the @mention function to work as expected.
Additionally, users can switch their IME (Input Method Editor) to English as this is not impacted.
The reply feature and @mention feature should now be working simultaneously and as intended.
・Current status: Out of an abundance of caution, we’ll continue monitoring the service to verify no additional impact occurs.
Concurrently, we ask that all users update their Microsoft Teams client to the most recent version to ensure the fix is applied.
Additionally, we are still waiting for customer confirmation that the issue has been mitigated.
Please reach out to support to confirm resolution.
・Scope of impact : This issue affects any Microsoft Teams user who has public preview features enabled and have set Japanese as the input language via IME in Teams.
・Start time : Thursday, September 16, 2021, 9:00 AM (12:00 AM UTC)
・Preliminary root cause : A recently introduced public preview feature, which adds the “reply” option to Microsoft Teams chats, contained a misconfiguration which was unexpectedly causing impact to @mention functionality.
・Next update by : Friday, October 22, 2021, 12:00 PM (3:00 AM UTC)

October 19, 2021 11:33 AM – Service restored

・Title : Some users are unable to @mention other users within Microsoft Teams chats when using the desktop client
・User Impact : User Impact : Users are unable to @mention other users within Microsoft Teams chats if using the desktop client with Japanese IME.
・More info : As a workaround, users can add a space after the “@” which should trigger the @mention function to work as expected.
Additionally, users can switch their IME (Input Method Editor) to English as this is not impacted.
The reply feature and @mention feature should now be working simultaneously and as intended.
・Current status : We’ve finished deployment of the fix to all affected environments.
To ensure the fix properly resolves impact for your users, all users will need to update their Microsoft Teams client to the most recent version.
We’re actively monitoring the service to ensure there is no residual impact. In parallel, we’re reaching out to reporting customers to confirm mitigation.
・Scope of impact : This issue affects any Microsoft Teams user who has public preview features enabled and have set Japanese as the input language via IME in Teams.
・Start time : Thursday, September 16, 2021, 9:00 AM (12:00 AM UTC)
・Preliminary root cause : A recently introduced public preview feature, that adds the “reply” option to Microsoft Teams chats, is unexpectedly causing impact to @mention functionality.
・Next update by : Wednesday, October 20, 2021, 12:00 PM (3:00 AM UTC)

October 14, 2021 10:49 AM – Service restored

・Title : Some users are unable to @mention other users within Microsoft Teams chats when using the desktop client
・User Impact : User Impact : Users are unable to @mention other users within Microsoft Teams chats if using the desktop client with Japanese IME.
・More info : As a workaround, users can add a space after the “@” which should trigger the @mention function to work as expected.
Additionally, users can switch their IME (Input Method Editor) to English as this is not impacted.
At this time, the reply feature has been disabled to mitigate impact to the @mention feature.
・Current status : We’ve completed our initial validation phase and have confirmed internally that the fix is effective in allowing reply and @mention features to work simultaneously.
Out of an abundance of caution we’re continuing to validate with affected customers to confirm mitigation.
Concurrently we’re initiating deployment of the fix to a small portion of affected environment while we continue to monitor the service.
・Scope of impact : This issue affects any Microsoft Teams user who has public preview features enabled and have set Japanese as the input language via IME in Teams.
・Start time : Thursday, September 16, 2021, 9:00 AM (12:00 AM UTC)
・Preliminary root cause : A recently introduced public preview feature, that adds the “reply” option to Microsoft Teams chats, is unexpectedly causing impact to @mention functionality.
・Next update by : Tuesday, October 19, 2021, 12:00 PM (3:00 AM UTC)

October 12, 2021 10:01 AM – Service restored

・Title : Some users are unable to @mention other users within Microsoft Teams chats when using the desktop client
・User Impact : User Impact : Users are unable to @mention other users within Microsoft Teams chats if using the desktop client with Japanese IME.
・More info : As a workaround, users can add a space after the “@” which should trigger the @mention function to work as expected.
Additionally, users can switch their IME (Input Method Editor) to English as this is not impacted.
At this time, the reply feature has been disabled to mitigate impact to the @mention feature.
・Current status : We’re continuing to perform extensive testing and validations for our proposed fix.
We are extending our testing process to ensure there is no unintended impact to the service.
Based on our current progress, we expect our initial validations to be completed by our next update.
・Scope of impact : This issue affects any Microsoft Teams user who has public preview features enabled and have set Japanese as the input language via IME in Teams.
・Start time : Thursday, September 16, 2021, 9:00 AM (12:00 AM UTC)
・Preliminary root cause : A recently introduced public preview feature, that adds the “reply” option to Microsoft Teams chats, is unexpectedly causing impact to @mention functionality.
・Next update by : Thursday, October 14, 2021, 12:00 PM (3:00 AM UTC)

October 6, 2021 10:37 AM – Service restored

・Title : Some users are unable to @mention other users within Microsoft Teams chats when using the desktop client
・User Impact : User Impact : Users are unable to @mention other users within Microsoft Teams chats if using the desktop client with Japanese IME.
・More info : As a workaround, users can add a space after the “@” which should trigger the @mention function to work as expected.
Additionally, users can switch their IME (Input Method Editor) to English as this is not impacted.
At this time, the reply feature has been disabled to mitigate impact to the @mention feature.
・Current status : We’ve developed a long-term solution that we expect to fully restore the reply and @mention feature for Japanese IME users.
We’re performing extensive internal testing to ensure there is no residual impact from our fix prior to deployment to the impacted environments.
We will provide an updated timeline once our validation is complete.
・Scope of impact : This issue affects any Microsoft Teams user who has public preview features enabled and have set Japanese as the input language via IME in Teams.
・Start time : Thursday, September 16, 2021, 9:00 AM (12:00 AM UTC)
・Preliminary root cause : A recently introduced public preview feature, that adds the “reply” option to Microsoft Teams chats, is unexpectedly causing impact to @mention functionality.
・Next update by : Tuesday, October 12, 2021, 12:00 PM (3:00 AM UTC)

October 1, 2021 11:19 AM – Service restored

・Title : Some users are unable to @mention other users within Microsoft Teams chats when using the desktop client
・User Impact : User Impact : Users are unable to @mention other users within Microsoft Teams chats if using the desktop client with Japanese IME.
・More info : As a workaround, users can add a space after the “@” which should trigger the @mention function to work as expected.
Additionally, users can switch their IME (Input Method Editor) to English as this is not impacted.
At this time, the reply feature has been disabled to mitigate impact to the @mention feature.
・Current status : We’ve received inconclusive reports from some affected users of our current solution.
We’re incorporating these reports into our investigation and we’ll continue to analyze and troubleshoot our solution efficacy to allow both reply feature and @mention feature to work simultaneously.
・Scope of impact : This issue affects any Microsoft Teams user who has public preview features enabled and have set Japanese as the input language via IME in Teams.
・Start time : Thursday, September 16, 2021, 9:00 AM (12:00 AM UTC)
・Preliminary root cause : A recently introduced public preview feature, that adds the “reply” option to Microsoft Teams chats, is unexpectedly causing impact to @mention functionality.
・Next update by : Wednesday, October 6, 2021, 12:00 PM (3:00 AM UTC)

September 30, 2021 10:46 AM – Service restored

・Title : Some users are unable to @mention other users within Microsoft Teams chats when using the desktop client
・User Impact : Users are unable to @mention other users within Microsoft Teams chats when using the desktop client.
・More info : As a workaround, users can add a space after the “@” which should enable the @mention function to work as expected.
At this time, the reply feature has been disabled to mitigate impact to the @mention feature.
・Current status : We’ve developed a solution that will properly allow the reply and @mention feature to work as expected for users that have their Teams language set to Japanese.
We’re performing extensive testing to ensure there is no unintended impact to other parts of the service prior to deploying it to the affected users.
In parallel, we’re reaching out to some of the reporting users to gain a better understanding of the scenario in which the @mention feature may not be working as intended.
・Scope of impact : This issue affects any Microsoft Teams user who has set Japanese as the input language in Teams and using this feature.
・Start time : Thursday, September 16, 2021, 9:00 AM (12:00 AM UTC)
・Preliminary root cause : A recently introduced public preview feature, that adds the “reply” option to Microsoft Teams chats, is unexpectedly causing impact to @mention functionality.
・Next update by : Friday, October 1, 2021, 12:00 PM (3:00 AM UTC)

September 28, 2021 10:53 AM – Service restored

・Title : Some users are unable to @mention other users within Microsoft Teams chats when using the desktop client
・User Impact : Users are unable to @mention other users within Microsoft Teams chats when using the desktop client.
・More info : As a workaround, users can add a space after the “@” which should enable the @mention function to work as expected.
The reply feature is currently in public preview.
・Current status : We’ve confirmed with some of the reporting tenants that the issue has been mitigated.
We’re working on a long-term fix to properly resolve the problem. If your users are continuing to see impact related to this event, please file a support ticket and reference this SI post for quicker mitigation.
・Scope of impact : This issue affects any Microsoft Teams user who has set Japanese as the input language in Teams and using the public preview feature.
・Start time : Thursday, September 16, 2021, 9:00 AM (12:00 AM UTC)
・Preliminary root cause : A recently introduced public preview feature, that adds the “reply” option to Microsoft Teams chats, is unexpectedly causing impact to @mention functionality.
・Next update by : Thursday, September 30, 2021, 12:00 PM (3:00 AM UTC)

September 25, 2021 11:51 AM – Service restored

・Title : Some users are unable to @mention other users within Microsoft Teams chats when using the desktop client
・User Impact : Users are unable to @mention other users within Microsoft Teams chats when using the desktop client.
・More info : As a workaround, users can add a space after the “@” which should enable the @mention function to work as expected.
The reply feature is currently in public preview.
・Current status : We’ve received reports that the initial mitigation effort did not resolve the impact as expected.
We have corrected the issue and re-disabled the reply feature. We recommend users to restart their Teams clients to receive the new changes.
We’re reaching out to some affected tenants and monitoring the service to validate the new solution is effective over the weekend.
・Scope of impact : This issue affects approximately 10% of users in Japan who have are using the public preview feature and impact is specific to users with their system language set to Japanese.
・Preliminary root cause : A recently introduced public preview feature, that adds the “reply” option to Microsoft Teams chats, is unexpectedly causing impact to @mention functionality.
・Next update by : Tuesday, September 28, 2021, 12:00 PM (3:00 AM UTC)

September 24, 2021 12:06 PM – Service restored

・Title : Some users are unable to @mention other users within Microsoft Teams chats when using the desktop client
・User Impact : Users are unable to @mention other users within Microsoft Teams chats when using the desktop client.
・More info : As a workaround, users can add a space after the “@” which should enable the @mention function to work as expected.
The reply feature is currently in public preview.
・Current status : Our internal validation determined that disabling the reply feature was effective in mitigating impact to the @mention functionality.
However, we are waiting for customer confirmation and we’ll continue to monitor the service to ensure no residual impacts occur.
・Scope of impact : This issue affects approximately 10% of users in Japan who have are using public preview and impact is specific to users with their system language set to Japanese.
・Preliminary root cause : A recently introduced public preview feature, that adds the “reply” option to Microsoft Teams chats, is unexpectedly causing impact to @mention functionality.
・Next update by : Saturday, September 25, 2021, 12:00 PM (3:00 AM UTC)

September 22, 2021 8:00 PM – Service restored

・Title : Some users are unable to @mention other users within Microsoft Teams chats when using the desktop client
・User Impact : Users are unable to @mention other users within Microsoft Teams chats when using the desktop client.
・More info : As a workaround, users can add a space after the “@” which should enable the @mention function to work as expected.
・Current status : We’ve identified that a recently introduced feature, that adds the “reply” option to Microsoft Teams chats, is causing impact.
We’re disabling the feature for a select group of users to mitigate impact to @mention functionality.
Additionally, we’re analyzing the impacting feature to develop a fix. During this time, we recommend any users still impacted by this issue try our provided workaround.
・Root cause : A recently introduced feature, that adds the “reply” option to Microsoft Teams chats, is unexpectedly causing impact.
・Next update by : Friday, September 24, 2021, 12:00 PM (3:00 AM UTC)

September 22, 2021 6:04 PM – Service restored

・Title : Some users are unable to @mention other users within Microsoft Teams chats when using the desktop client
・User Impact : Users are unable to @mention other users within Microsoft Teams chats when using the desktop client.
・Current status : We’re analyzing trace logs from affected users to isolate the root cause of the issue.
・Scope of impact : Impact is specific to users located in Japan, that utilize the Microsoft Teams desktop client to @mention users in chats.
・Next update by : Wednesday, September 22, 2021, 8:00 PM (11:00 AM UTC)

September 22, 2021 5:40 PM – Service restored

・Title : Some users are unable to @mention other users when using the Microsoft Teams desktop client
・User Impact : Users are unable to @mention other users when using the Microsoft Teams desktop client.
・Current status : We’re reviewing support case details to determine the next troubleshooting steps.
・Scope of impact : Your organization is affected by this event, and the problem may impact any Microsoft Teams desktop client user.
・Next update by : Wednesday, September 22, 2021, 7:30 PM (10:30 AM UTC)

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