For Windows 2012R2 (RDS) I have found that the Teams credential information is stored in %LocalAppData%\Microsoft\IdentityCache. Steps that worked for our users with sign in issues:

Close Teams and Outlook completely (Exit through the systray icon)
Remove %APPDATA%\Microsoft\Teams (Teams cache)
Remove the subfolders under %LocalAppData%\Microsoft\IdentityCache (in our case there was only one folder named ‘1’).
Restart Teams
For us this removed any cached Teams settings as well as any cached login information for Teams. After that Teams runs through the sign in dialog from the start.

If you just want to delete the stored credential, clearing the IdentityCache may be enough without clearing the Teams cache. I have not tried that.

Try at your own risk, of course. You may be deleting other stored credential information as well, so I recommend creating a backup of the profile first.