Since the beginning of the year. For three accounts. Been working fine. No password issues.

Was trying to set up one of my emails on a different account on my computer.
The IP/email is frontier but it’s “powered” by yahoo.
I put in all the same settings put in my email and it wouldn’t take it it still worked on the other one
Finally it took it by doing the Auth2 ( a password that is for that account only ) I don’t remember doing it quite like that when frontier first went to Auth2 in this case when your using a third party like thunderbird.)
Only thing is if I went to the login page at frontier it accepted my actual password and not some random generated one for the Thunderbird Auth2.
So that is a bit different than your thing.
Possibly try login page again, forget password reset.
And then try to reset thunderbird with the Auth2 password when it asks. You use the one for thunderbird and one for the web login.
I’m not really good at explaining this I’m actually somewhat of a computer struggler.
So hopefully it makes sense and I didn’t tell you something you already knew.
Good luck at getting your emails to down load into thunderbird.