What version of Firefox and OS are you using? What other security software do you have installed?

I have Firefox 134.0.2 and it is up to date My operating system is Windows 11 and it updates regularly. I have McAfee and Malwarebytes

I have the same problem - yesterday I stopped being able to log in. I can log in with <shudder> Edge </shudder>, but I hope that's just a temporary solution.

I'm on Firefox 134.0.2 64-bit, Windows 10 fully updated.

I know what you mean re "Edge" Not my favorite. Fingers crossed that Firefox will figure it out soon as it is probably not an issue with AT&T (yahoo/sbcglobal etc) since it works on my cell phone on Chrome and Firefox there and also works on Edge. I really do not want to stop using Firefox but it is inconvenient to go back and forth between Edge and Firefox. Third day of this. Fingers crossed and sending positive energy to Firefox to correct this issue!

It works for me. see screenshot

Do you have the same issue with Firefox in Troubleshoot Mode? https://support.mozilla.org/en-US/kb/diagnose-firefox-issues-using-troubleshoot-mode#w_how-to-start-firefox-in-4troubleshoot-modesf5safe-modesf

Did you try clearing the browser cache? https://support.mozilla.org/en-US/kb/how-clear-firefox-cache#

I clear the cache in history every day and I've done it at least 10 times today. That did nothing. I did try opening Firefox in the troubleshoot mode as you suggested and first try of logging in for email it gave me a message stating log out was successful, but then showed the sign in screen again and then it worked. Does this mean I need to start firefox in troubleshoot mode each time. As nothing was "troubleshooted" unless it does it automatically. Thank you for the suggestion. At least I know I have a way to open my email on Firefox. Not sure why it happened for the last 3 days. I have used firefox as my browser for so long I don't even recall when. It was at 15 years. Never had an issue like this.

I cleared the cache after closing down Firefox in troubleshooting mode. Then tried opening it in regular mode. Same error popped up. I log into my email (I have two of them, so I logged into one at a time.) Same thing. It automatically logs me right out and then sends an error code. I am doing nothing different than I have since I had these emails 15-20 years ago. Then I went back to trouble shoot mode. Clicked on items for troubleshooting but do not understand all of the "lingo". Will have to ask my son who does IT for a living to see if he can figure out a permanent fix. I usually can muddle through but this is not working except in the troubleshooting mode. ATT denies it is their issue. But why it happened after all these years is beyond me. If anyone has any other ideas, please let me know. Thanks.

I too have this problem that just started about 2 days ago also. I get to the login screen, enter id and password hit enter and on the tab I see logout successful and go to a screen with the following message: Something's gone wrong We may be having trouble with your connection. Connecting your device to Wi-Fi could help fix the issue or try again later. If you were using an app, close this page. Otherwise, start over.

I do not have this issue in Edge or Chrome.

I have followed all the steps tried by previous users clearing cache etc. without success too.

Yes, the problem does not occur in safe mode, but I shouldn't have to do that. After doing so I experimented with disabling the addons individually. I only have Rapport and DuckDuckGo Privacy Essentials. Lo and Behold, the problem is with DuckDuckGo. I reported the problem to them and hopefully they will find a fix. As a workaround, I disabled Privacy Essentials for the login page and I can now log in.

I guess I am definitely not alone on this one. Hope that Firefox can resolve as I too do not want to use Edge forever. Must have something to do with updates tho the last update was several weeks ago and the issue didn't start til 3 days ago for me. My phone does not update with Firefox browser so I can still access my email on my cell phone as well as by going to Edge on my computer.

The Duck Duck Go setting seems to be the culprit. I turned it off for this page and was able to log right in. Here's hoping Duck Duck Go will figure out what needs changing.

Cheers for the tip!

How do I turn off Duck Duck go for accessing the email? I didn't try that yet. Was clearing ice and snow outside.

At the top right of your browser is a Duck Duck Go icon - just left of the hamburger menu. On the login page where you have the error, click the icon and there's a switch there to turn it off for the page where you are. I did that and it let me log in immediately.

I found it. My screen had a different set up but I was able to get to it. I guess whatever I did removed Duck Duck Go completely as I closed and reopened Firefox and Duck Duck Go is now replaced with Google search engine. Everything works ok now. Too bad as I liked Duck Duck Go but the aggravation is not worth it for now. Thank you to all of you for your advice and input.

On the ATT Mail login page, in the upper right corner, there is an extesion icon. Click on it and it will diplay your extensions. Click on Privacy Essentials and you will see where you can turn it off for that particular site.

That's what I did and the only option there deleted the browser not just the extension. It's gone from all websites in Firefox now. I need to just let this be for a few days. I have a lot of things to do re fixing up my house and getting year end tax paperwork ready for CPA. Thank you for your help.