It's an exact duplicate of an archived question that didn't have a solution.

"Error message on only one of my four gmail accounts.

"The STAT command did not succeed. Error getting message number and sizes. Mail server pop.gmail.com responded: Invalid credentials."

nothing has changed in my settings, yet this problem continues to present. need some help, please. "

The suggestion then was to set OAuth2 and that's what I did.

The suggestion then was to set OAuth2 and that's what I did.

That has been the required authorization method for gmail for some time. See https://support.mozilla.org/en-US/kb/thunderbird-and-gmail

As of May 30, 2022, Google no longer allows Less secure apps access for Gmail accounts, thus OAuth is required. If you are using Google supplied “app passwords“, Thunderbird version 91.8.0 and newer will make that conversion for you. Further, Gmail accounts do not work with Thunderbird 31 and older because they do not support Google's OAuth

Yes, I know that. But my issue is that even with the setting set to OAuth2 I get a message about wrong credentials and no re-try of any kind to allow me to change anything.

The simple solution was to open Settings and look for a saved password and then delete that to try again. This worked.

However, possible improvement.

TB should probably offer that as an automatic choice in the error message. Such as "reset/delete saved password and try again?"