Using Classic Outlook on Windows for personal email, calendar, and contact management
Hi! First, fully close Outlook. Then sign in to the affected Gmail account in a browser, open Google Account > Security > Your connections to third-party apps & services, select Microsoft apps & services, choose See details, and then Remove all access. This removes the old consent so Outlook can ask again with the correct permission prompt. Next, Open Credential Manager from the Start menu, go to Windows Credentials, scroll to Generic Credentials, and remove the entries that start with MicrosoftOffice16_Data:OAUTH2 and include tp_google_imap_Oauth2. After that, reopen Outlook and either use the Sign in via browser prompt or add the Gmail account again. During the Google sign-in page, make sure the checkbox is selected for Microsoft to read, compose, send, and permanently delete Gmail mail; that permission is what allows the connection to complete successfully.