Start here. Let us know how it goes. If you're facing any errors, kindly specify the error message or post a screenshot.

Thank you very much, for the detail of my problem, when I "add" an email account, I therefore enter the email address and the password correctly.

When I do "continue" it does show me that the "configuration found in Mozilla ISP database"

I checked all the same the available configuration which is correct in IMAP. I do "done", and it opens the window that I attached in screenshot to connect. When I enter my email address and click Next. Nothing happens, he reloads the page, constantly asking me for my email address, I'm blocked.

I tried to go to Gmail settings by activating IMAP access and POP access. In Account Settings I went to Security and turned off 2-Step Verification. I even enabled access to less secure applications which was noted in Google's help. I don't know what else to do to make it work.

Tell me if anything else is needed.

Open Preferences > Privacy & Security > Web Content and make sure Accept cookies from cites option is enabled. Set Accept third-party cookies to Always and Keep until to they expire. Cookies must be allowed for signing in via that window to work.

When the email address is not automatically entered in the OAuth window and it goes in an endless loop, it usually means cookies are not accepted in TB Preferences/Privacy & Security. That's required for OAuth authentication to complete.

I forgot to mention that I already had an email address registered in Thunderbird and that I had no problem with it. I disabled and re-enabled cookies as you advised me, but nothing changed. I noticed that I had a problem in my computer's files two Thunderbirds were installed. I uninstalled and reinstalled Thunderbird properly, everything is fixed. I apologize for the inconvenience and thank you very much for your help, I should have noticed it before.

Again, thank you for your help and your time.