Hi @James James
According to your case description, you encountered the problem that the user in Microsoft Teams is displayed as an "unknown user".
Could you please tell me if the user is one of the following.
- Deleted user account
- Disabled and re-enabled user account
Are all Teams functions of the user normal? Have you tried to log in to the Teams web client to see if it is also displayed as an "unknown user"?
In addition, please refer to the following steps that may solve this problem:
Clear Teams cache:
Check account settings:
Make sure that the user's account settings in Microsoft Teams are configured correctly. You can do this by clicking the profile picture in the upper right corner of Teams, selecting "Edit Profile" and updating their information.
- If not, you need to contact the global administrator to log in to the Microsoft 365 Admin Center. The administrator can edit the information and reassign Teams licenses for the user by clicking "Users", selecting the user. Click Office 365 E3/E5 > Licenses, etc., > Microsoft Teams to do this.
- Check if the Teams user's account is active in Azure Active Directory (AAD). Sign in to the Azure Admin Center with an administrator account, select Users, check the user's active status, and re-enable the user. (Also applies to Guest users)
- After performing the above operations, wait for synchronization. New or reactivated users may appear as "Unknown User" in Microsoft Teams chat for a few days after activating their account in Azure. The problem usually resolves itself after a few days.
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