Hi @R H
Could you please tell me:
- Have you added another account in the Teams client and used the correct identity to log in to the Teams client?
- Have you tried to use the Teams web client to verify whether the problem still exists?
- Do you get any error code message when you try to log out of Teams?
Based on the case description you provided, it is recommended that you use the Windows registry key to turn off the pre-population of UPN, refer to this.
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.