I got my teams running again after some time. In my experience (with Beta 6), the credentials stored in Teams are corrupt. When I logged in with my personal account (not business account) I was able to use Teams. Unfortunately it is not possible to remove the credentials by clearing the cache. In my case, I uninstalled Office, cleared the cache, removed entries in the keychain, restarted the Mac, and then reinstalled the entire Office suite. My credentials were still saved, but it asked me for a password again. After entering the password, I was able to log in again. I know that these tips are of limited help. But after about 3 hours of research I got it running :-) BTW: MBP 13" (Apple Silicon, M1)