Outlook on Windows suddenly stopped connecting to Gmail on more than one computer. Deleted and tried to re-add the account which generated the message in the screenshot below.
What was required was removing the OAUTH2 credentials as outlined below:
how to clear the Google IMAP OAuth credentials when multiple accounts - Microsoft Q&A
We weren't able to set up your google account with imap. Instructions available say to clear the Google IMAP OAuth credentials. I have multiple google email accounts & can't identify the one to delete.
(learn.microsoft.com)