Using older versions of Outlook for Mac in business environments
Just had this issue crop up - July 2023 - I tried the various options mentioned over this long thread, including most recently the option within accounts to 'reset' the account via the 3 dot menu option at the bottom of the accounts list. That did NOT work for me. I finally did what I view as the nuclear option, and (instead of the 3 dots, but same location under the accounts) deleted my email account, and then re-added it. That finally did resolve the issue.