In some cases, it works for the YouTube Firefox problem. Note: This message was sent on a different computer & browserFirefox safe mode is a special Firefox mode that can be used for tackling issues caused by some extensions, hardware acceleration, and parts of other features. I have WebRoot on my computer due to my job, and I asked our IT staff if they could see WebRoot blocking anything related to Firefox on their end. Things I have tried for troubleshooting already: Version 20H2 at start of issue (updated to 21H2 during troubleshooting) while trying to uninstall Firefox or delete certain files, I would get a warning to 'close Firefox first' or 'can't perform this action while app is running.' After seeing these, I would again confirm that Firefox appears closed and Task Manager shows no related tasks. I have listed my steps to troubleshoot below, but I want to note one weird thing I observed: Even when Firefox is closed, and Task Manager doesn't show any Firefox processes open, my PC seems to think Firefox is running. So it seems to be an issue just with Firefox. Everything else that it is internet or cloud based on my PC is running fine too. I tried opening Chrome, and it ran just fine. This morning I found Firefox was still not loading anything, although my internet connection was fine. I did not see anything (apps, etc) on my PC updating. I assumed it was an internet issue as I did see my internet connection get disrupted once or twice. New tabs would also not load any content.

Around 8 or 9pm, I first noticed that none of my open tabs were loading any content, and the tabs had the 'loading' animation playing. Yesterday, I had Firefox open all day (I usually have my computer on all day), and it was working fine. I also couldn't access the Settings at all (clicking on Settings in the browser menu produces no results or feedback.) New windows and tabs would not load any content.

Last night, for some reason it simply ceased to work. I've been running Firefox successfully on my Windows 10 PC for a long while now. Hey folks, hopefully you can help with this mysterious issue!

Mozilla firefox not responding win 10