I've been mulling over this for some time and can't get my Google OAUTH2 settings to act predictably.
Attached screenshots to show my settings. Everything works if I manually re-authenticate in edit app. In preview mode user gets an Authentication Loop.
If I disable "Enable an auth verification endpoint" the loop goes away but user has to manually re-authenticate. I don't see an option to automatically run an auth workflow here either.
Also in auth configuration page "See Token Status" says Access Token is granted but not Refresh or ID Tokens.
Ideal behaviour permanent authentication for all users once I manually retrieved Access and Refresh Tokens. Alternatively they could each authenticate once than token refreshes.