Is your authentication method in account settings set to oauth2? It needs to be.

Yes authentication method is set to OAuth2. Connection method SSL/TLS

Hello Matt

I am at a loss to know what I have done wrong.

I have deleted Thunderbird from my Mac and reinstalled. The Set Up Exisiting Email address page comes up. Name, address, password filled in and available configurastion found in ISP server. Select 'Done' and message is "Unable to Log in at server. Possible wrong configuration, username or password. "

I am not sure password is correct. Is there any way I can edit or change password?

I have tried everything I know to log in to server but nothing works. I have been usingThunderbird for many may years and do not wish to change the email address. Cannot figure out if my name is not what is on server, configuration is wrong even though it shows on IMAP as found on server, or password. When I look at password it does not show a password, just a stream of data

oauth uses tokens. Once you use your password in the initial authorization, there is no further use of that password, all future interactions with the server are managed and authorized through the generated tokens.

My guess is, and it has to be a guess as I really only know you are using gmail, is that

• You have perhaps revoked Thunderbird authorization in your settings on Google.
• You have a software firewall that is blocking communications, These things generally rely on knowing the executable name and versions and blocking everything else. Not very helpful when an update occurs.
• You have another third party software installed that is blocking connection attempts. (antivirus are good for that)
• You are using a VPN. They are very very prone to causing mail connection failures.

Matt---I have the same issue. When I log in that message pops up. I click OK and I'm good to go. But, when I check messages, the same message pops up. Now, I can see that messages are downloadling but I have to click OK to open them. I have had multiple updates to Thunderbird, and none of them fix the problem. I tend to think that one of the updates caused this problem as I had zero issues with Thunderbird before and now I do. Since I receive messages, I don't think that anything in Google is an issue. I do not have a software firewall. I have not downloaded any new antivirus programs. No VPN. This is more of an annoyance that anything else, but it is an annoyance. Other than uninstalling and then reinstalling Thunderbird, how can I get this issue to go away? TIA.