If this is a new account, I suggest deleting it completely and starting over. Create the account and DO NOT insert password, and also check to be sure that settings>privacy&security is set to allow cookies. And do not enter password until Google requests it.

No, this is not a new account, I have had if for many years and has always been flawless. I am not a computer expert so looking for help in getting it working again. Thanks

Thunderbird only has the last password you provided. If the password no longer works, that would imply the email provider has changed security practices, or that your thunderbird profile is corrupted. Restoring a backup might address that issue, but contacting your email provider seems the best approach to reset the password.