The answer is obvious as it is in the posted information. '''invalid credentials.''' So I suggest you check your gmail account settings in account settings and ensure they are correct. Things like your user name being set to your gmail email address, your authorization method being set to oauth2.0 because clearly your currents credentials and no longer valid according to Google. Perhaps try logging into your google mail using your browser and see if there is anything of note from google about your access. I see you posted another topic. Forget it. Google are complaining about your credentials. I doubt the version of Thunderbird has anything to do with it at all.