I have no idea what "the suggested actions" are or whose suggested actions they were. Please, we know exactly what you tell us. In this case just about nothing except you have issues with yahoo.

Note this URL is on your computer. No where else. That is what localhost means.

What I do know is Yahoo are having issues. They are exceedingly coy about exactly what the issue is, and their suggestion of removing and replacing a password make no sense to me at all. But they are the ones with an issue they so far are not explaining so we can only follow their instructions.

After watching their video I am guessing their oauth database has been lost, perhaps hacked, so they need to establish new keys, hence the re-authentication. Normally the server would refuse the old key and a new one would be generated by going through the re-authentication process. But do it their way. So you will be removing an Auth:// entry in your password manager in Thunderbird with a user name of your yahoo account.

Note that password management instructions for Thunderbird are here https://support.mozilla.org/en-US/kb/password-manager-remember-delete-change-tb

If you ring Yahoo do not remove any pop mail accounts, even if they tell you to do so. They like to tell you to remove the account and loose all the mail for the last however many years and just sort of hang up when you complain about the standard of support after referring the person here for some volunteer to try and glue the mess they made back together again.

To quote yahoo from this page https://help.yahoo.com/kb/SLN4075.html

We are aware some users are experiencing issues accessing their Yahoo Mail using third-party mail clients. Removing and re-entering your Yahoo Mail password or app password in the email client should solve this. Read our help article for more information and steps. You may also access Yahoo Mail on the web at mail.yahoo.com or using the Yahoo Mail app for iOS or Android.

Their support article linked to is here https://help.yahoo.com/kb/mail/SLN36847.html

Final Note: Antivirus programs (other than defender) are know to cause issues with the authentication process at the step where the results are passed back to your local machine via localhost. You may need to disable third party antivirus if that is your issue.

This is a 5 month old question, but as I'm new here and am about to beg for help with a different problem maybe I can save someone who finds their way here the two full days it took me to solve this one.

I'd upgraded from a very old Thunderbird 102.14.0, first to 128.8.0 but then thinking that was the problem back down to 115.16.2. Didn't matter -- my Thunderbird POP and SMTP to Yahoo mail which had worked flawlessly for years was completely broken.

I read dozens of Yahoo, Mozilla, and third-party help pages including Yahoo POP settings and Thunderbird and Yahoo. I tried dozens of combinations of settings: SSL/TLS vs STARTTLS, Normal password, Encrypted password, Oath2, ports 995, 465, 587, and even changing to IMAP (which I hate) on 993. Nothing worked. And of course I could still log in and access Yahoo mail via Firefox. I also knew it wasn't a firewall or anti-virus problem because Thunderbird still worked doing POP/SMTP with my other, non-Yahoo, accounts.

Bottom line is that the online help/instructions were misleading. They stated things like, "If you try to use Yahoo Mail in a third-party email client using less secure sign-in technology ..." and "Third-party email apps (that do not use our Yahoo branded sign-in page) ... you'll need to generate and use an app password." There was even one which specifically said this was only necessary if "you don't normally use a password with Yahoo mail."

I forgive myself for misunderstanding all of it because, a) What's "less secure" about SSL/TLS/STARRTLS technology? b) I always needed a password for Yahoo mail, and c) Thunderbird had always worked with that one.

But either something changed on exactly the day I upgraded my Thunderbird, or the older one somehow ignored/worked around this "app password" requirement. Right now, with Yahoo and current Thunderbird versions it's absolutely necessary to generate an app password by logging onto your Yahoo account, navigating to Security, and clicking the "Generate and manage app passwords" link. Use the one it creates (not your normal one) when Thunderbird fails to connect and asks for a password, and a pre-existing POP/IMAP/SMTP configuration or a new one as per the normal setup instructions in the links above should work.

Again, I hope this saves someone the pain I went through.