This is the error message in English: "We could not sign you in. Try again from a different device."

Hier ein ähnlicher Fall / Looks like this is a similar issues: https://www.thunderbird-mail.de/forum/thread/97589-einrichten-von-yahoo-mail-konto-unm%C3%B6glich-etwas-ist-schiefgelaufen/?postID=563425&highlight=yahoo#post563425

Hello there

Give that browser access to use Javascript. Using heavy antivirus can control these log in processes . Turning of these antivirus and look for a possible clue , try to use it now and log in. This is how to check for the browser. Try to update all involved parties. Did you see all settings for the Smtp ,they where all oke?

I've checked SMTP again: smtp.mail.yahoo.com, Port 465, normal PW, SSL/ TLS. Javascript: enabled.

I've tested App_PW as well.

The answer is: "We could not sign you in. Try again from a different device."

When I copy the log-in-link to Chrome, I can proceed the process and agree to the access of Thunderbird to my yahoo account. But after that there is another error-message. I can add some screenshots later.

Hello there

Yes okay , show me all these errors of that or these issue s , are you sure that you do have more issues? https://support.mozilla.org/en-US/kb/how-to-make-screenshots Can you use recovery mode for these accounts?

Hello there

You can try to change port numbers. 465 into 587. Use Start/tls. Linux programs also can use these settings with email clients.

Enclosed you'll find two screenshots. The Firefox error message is "We could not sign you in. Try again from a different device." I had deleted cache, history before. The Thunderbird error message is: "Could not log you in. Maybe something is wrong with settings, pw or username."

Hello there

The use of antivirus can be interrupting these settings try to turn them off for a while and firewalls or similar look a like software to.

Before making such changes. Make back ups if possible before.

Be sure that passwords usernames inlog fields are filled in correct. Old user names are possible present try to change them as asked.

Hello there

To change that pop account from pop Imap is to deactivate that pop account but do not delete it . Try to fill in that password but incorrectly the incoming email for that account stops with receiving mail. Do not delete that account yet.

Create new account  : with that existing account go to create that account with imap protocols now.

You do get pop ups now from thunderbird or from something else? Can you send me that? https://support.mozilla.org/en-US/kb/how-to-make-screenshots Now you did try the automatic way to create a pop account to that new Imap account. Is that possible?

What is blocking? It might be that antivirus software and the other mall ware software is buttering there if that software is installed on that pc including that ask for recheck of passwords and user names older usernames can be changed to if possible.

Is that linux version compatible with all of the other programs? What versions do you use Thunderbird / Linux / windows / security software / others. Can i ask?

Linux: Ubuntu 24.04.3 LTS. Browser: Firefox 145.0.1 (does work in a virtual box with Ubuntu 24.04.2 Thunderbird: 140.4.0esr - Thunderbird works when I enter the App-PW from Yahoo!

Hello there

There went a package change in Linux can you restore that first? That change can made this mess? Did you hear about snap or apt packages that has been changed , they can really do bad to thunderbird usage if these normal version had updates and had been changed .