When entering the login data for the Teams login in the XPhone Client, incorrect data was stored and you can no longer delete it or the window for entering the login data no longer opens.
For all possible solutions, we assume that the check mark in the Connect Client under Configuration > Presence > Synchronisation options... > "Remember login data" is removed. If necessary, do this later:
First close the Connect Client.
Then check in the Windows Control Panel under Logon Information Management > Windows Logon Information whether Teams entries are stored there.
If so, remove them and restart the Connect Client. Then check whether a new entry of the Teams credentials in the client is possible again.
Start the Teams Client and the XPhone Client.
Then log off and log on again in the Teams Client and check whether the correct Teams account is now stored in XPhone or can be stored again.
Note: Repair installation and reinstallation do not help here.