Hi sfhowes, I have the 3 items set as you describe, and have reviewed the article you linked. I have followed the settings for IMAP and SMTP as described there, but am still getting the same response. Am I supposed to be getting a Gmail login screen when using OAuth2? Because I am not seeing that, just the configuration could not be verified message. My default browser is Firefox, and I have popups unblocked there.

Hmmm...I don't have any extensions that should block Javascript. And I would think the AV program would say something if it was blocking access. Is there a trace or something in TB that might show how far I am getting?

Verified that Javascript is enabled. Tried to run setup in safe mode, but still the same problems. I do have an account built in TB with the proper Gmail address, servers and ports, etc, as they should be - sometimes happens when I set up with manual config. But it times out when trying to retrieve mail and won't send anything.

Further note - my Gmail account is new, less than a month old. In the linked tips doc above it mentions something about an account that is less than 90 days old. Could this be a factor?

Finally got this configuration to work. My ISP also works with TB - the tech suggested setting up 2-step verification then generating an app password to use for Windows PC mail. Still took a little tinkering, but the default ports and servers seemed to work.

That may well be. I never did understand what the problem really was, so I couldn't say one way or the other. But I do appreciate your help along the way.