Accessing and using Microsoft Teams on smartphones and tablets across platforms
To help narrow down the issue, could you first check whether you can sign in to the same account through Teams on a computer or Teams on the web?
In the meantime, you can try the following:
-Make sure Teams is up to date.
-Restart your phone and try signing in again.
-Go to Settings > Apps > Teams > Storage and select Clear cache.
-If the issue persists, uninstall and reinstall the Teams app.
Since your IT department is already looking into the issue, they can also check the Microsoft Entra sign-in logs for your account around the time of the failed sign-in. The sign-in details may provide more information about the cause of the failure.
They can also check whether any Conditional Access policies require an approved client app or an app protection policy for mobile access.
For more information, see: Conditional Access - Require approved app or app protection policy - Microsoft Entra ID | Microsoft Learn
Additionally, you can refer to the AI answer below for additional information that may be helpful in your situation.
I hope this helps. Please let me know if you have any updates.