Hi @amy low
To help you resolve this error, I need to know the error code that you are getting. You can find the error code on the Teams sign-in screen. It usually starts with 0x followed by some letters and numbers. For example, 0xCAA20003 or 0xCAA80000. Can you please tell me the error code that you see?
You can also use the following steps to troubleshoot the problem:
Contact your admin to use the diagnostic tool in the Microsoft 365 admin center.
If the diagnostics didn't detect any issues, but you still can't sign in to Teams, or you don't have a Microsoft 365 admin account, select Download SaRA and start the test automatically.
In addition, you can also try to fix the problem manually according to the method provided in this document
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.