Are you experiencing the same issue in the Teams web client?
If the problem only occurs on the Teams desktop client, try clearing the Teams cache and restarting Teams:
If the issue occurs on both the Teams desktop client and the Teams web client, try the following solutions:
1.Run the Teams Sign-in diagnosticin the Microsoft 365 admin center. In the User Name or Email Address field, enter the email address of the user who's experiencing the Teams sign-in issue.
2.If the diagnostic doesn't detect any issue, but you still can't sign in to Teams, or you don't have a Microsoft 365 administrator account, download SaRA and automatically start the tests.
3.At the same time, you can also try to fix the problem manually. Please refer to this document for detailed methods.
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