Open Keychain Delete all Entries with "Teams" Also delete all similar entries with "Microsoft" Maybe also delete everything mentioned here: https://techcommunity.microsoft.com/t5/microsoft-teams/microsoft-teams-on-mac-wont-let-me-change-log-in/m-p/2264480 Note to self: Microsoft Teams sucks big time. Beg every customer to please use any other available solution.