I don't know where you got the idea that Thunderbird and Google are collaborating against you. It's not true. Also, reinstalling Thunderbird rarely solves problems like this because all specific email account information is stored in your Profile, which a reinstall doesn't touch.

I advice would be to:

- Make sure cookies are fully allowed in Thunderbird;

- Remove all existing cookies for Gmail;

- remove all stored passwords for that Gmail account;

- restart Thunderbird. You should then be prompted for your credentials, and hopefully Gmail will like them.

I won't go into a lot of detail right now because it sounds like you have already made up your mind, but if you would like to try to work through this, please let us know.

Thank you for getting back to me. Your response coaxed me into making one more attempt. I Googled instructions for creating a new Thunderbird profile, did so, then reset my screen to a much reduced level of scaling. That allowed me to finally ee the 'allow Thunderbird to access Google' button at the very bottom of the screen. Completed the profile creation, and the app seems to be performing normally. As a gesture of appreciation for your taking time to respond to my query, I've made a modest contribution to Mozilla. Happy to do so, given the promptness of your message.