Did you try a new clean profile ?

See "Creating a profile":

• https://support.mozilla.org/en-US/kb/profile-manager-create-remove-switch-firefox-profiles

If the new profile works then you can transfer files from a previously used profile to the new profile, but be cautious not to copy corrupted files to avoid carrying over problems.

• https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile

Firefox shows a purple shield instead of a gray shield at the left end of the location/address bar in case Enhanced Tracking Protection is blocking content. You can click the shield icon for more detail and possibly disable the protection. You can check the Web Console for relevant-looking messages about blocked content.

• https://support.mozilla.org/en-US/kb/enhanced-tracking-protection-firefox-desktop
• https://support.mozilla.org/en-US/kb/smartblock-enhanced-tracking-protection
• https://support.mozilla.org/en-US/kb/trackers-and-scripts-firefox-blocks-enhanced-track

This could be a problem with the TLS 1.3 Early Data feature also known as Zero Round Trip Time Resumption (0rtt). You can try to set security.tls.enable_0rtt_data = false on the about:config page to disable this feature to see if that helps.

You can open the about:config page via the location/address bar. If you get the warning page, you can click the "Accept the Risk and Continue" button.

• https://support.mozilla.org/en-US/kb/about-config-editor-firefox

https://support.mozilla.org/en-US/kb/diagnose-firefox-issues-using-troubleshoot-mode

Safe Mode is a troubleshooting mode that temporarily turns off hardware acceleration, resets some settings, and disables add-ons (extensions and themes), any userChrome.css/userContent.css files, and some other advanced features to help you assess whether these are causing the problem. If the problem goes away, that tells us one thing. If it does not, that tells us something else.

It could be the work of one of your add-ons, or it could be Hardware Acceleration. How to disable Hardware Acceleration {web link}

Type about:addons<enter> in the address box to open your Add-ons Manager. Hot key; <Control> (Mac=<Command>) <Shift> A)

In the Add-ons Manager, on the left, select Extensions. Disable a few add-ons, then Restart Firefox.

Some added toolbar and anti-virus add-ons are known to cause Firefox issues. Disable All Of them.

If the problem continues, disable some more (restarting FF). Continue until the problem is gone. After, you know what group is causing the issue. Re-enable the last group ONE AT A TIME (restarting FF) until the problem returns.

Once you think you found the problem, disable that and re-enable all the others, then restart again. Let us know who the suspect is, detective.

I tried all the steps above and none of them fix the issue. The only thing that made it work again was running Firefox in Windows 8 compatibility mode.

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.

See "Visual Studio 2015, 2017, 2019, and 2022":

• https://docs.microsoft.com/en-US/cpp/windows/latest-supported-vc-redist
• https://aka.ms/vs/17/release/vc_redist.x64.exe
• https://aka.ms/vs/17/release/vc_redist.x86.exe

You may also have to install the Visual Studio 2013 Redistributable Package. You need to reboot the computer.