Are you on Linux, Windows, or Mac? What version of the browser? Have you tried safe mode? Firefox safe mode: Click the menu button, click Help and select Restart with Add-ons Disabled…. Firefox will start up with the Firefox Safe Mode dialog.

I'm on windows, Firefox doesn't open at all, I can't click on any menu button because the app itself doesn't open at all.

You can check for issues caused by a corrupted or incomplete Visual C++ installation that is missing runtime components (Redistributable Packages) required by Firefox, especially VCRUNTIME140_1.dll.

In that case, I would install both 32-bit and 64-bit "Visual Studio 2015, 2017 and 2019" downloads, (x86: vc_redist.x86.exe and x64: vc_redist.x64.exe) from https://support.microsoft.com/help/2977003/the-latest-supported-visual-c-downloads

I'm sorry but that didn't seem to work either. Those files are all installed, I tried to fix the old files but reinstalling them but that didn't work either.

Some problems occur when your Internet security program was set to trust the previous version of Firefox, but no longer recognizes your updated version as trusted. Now how to fix the problem: To allow Firefox to connect to the Internet again;

• Make sure your Internet security software is up-to-date (i.e. you are running the latest version).
• Remove Firefox from your program's list of trusted or recognized programs. For detailed instructions, see

Configure firewalls so that Firefox can access the Internet. {web link}

this doesn't seem to be the problem, the app still crashes on startup

If you can't get Firefox to open, you will have to do this the hard way. https://support.mozilla.org/en-US/kb/mozillacrashreporter

Open the file browser / explorer on your computer. Note: You may have to enable Show Hidden Folders / Files. Enter this in the address bar;

Windows: %APPDATA%\Mozilla\Firefox\Crash Reports\submitted Win 7/Vista: C:\Users\<username>\AppData\Roaming\Mozilla\Firefox\Crash Reports\submitted Win XP/2000: C:\Documents and Settings\<username>\Application Data\Mozilla\Firefox\Crash Reports\submitted Win 10: Press <Windows> + R on the keyboard. A Run dialog will open. In the Run dialog, type %APPDATA%\Mozilla\Firefox\Crash Reports\submitted <Enter>

Mac OS: /Users/<username>/Library/Application Support/Firefox/Crash Reports/submitted Linux: /home/<username>/.mozilla/firefox/Crash Reports/submitted

Copy the most Recent 5-7 File Names in the folder. Press the Reply button. Now go to the reply box and paste them in.

What happens under a different user account on that pc?

There doesn't seem to be any crash report on file, only installation reports

i have this exact same problem and none of these solutions have worked for me.

What happens under a different user account on that pc? Have you tried Windows in Safe Mode?