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}

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 and 2019":

• https://support.microsoft.com/en-us/help/2977003/the-latest-supported-visual-c-downloads
• https://aka.ms/vs/16/release/vc_redist.x64.exe
• https://aka.ms/vs/16/release/vc_redist.x86.exe

You may not need the latter (32-bit version) if you use 64-bit Firefox. You may have to reboot the computer.

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}

Unfortunately this only worked the first time. Firefox updated again and it will no longer work.

Did you try the Firewall again?

Did you try the Firewall again?

I just tried again and it seems to be working.

Do you mean the browser is working now? If so,

I am glad to hear that your problem has been resolved. If you haven't already, please select the answer that solves the problem. This will help other users with similar problems find the solution.

Thank you for contacting Mozilla Support.

Do you mean the browser is working now? If so, I am glad to hear that your problem has been resolved. If you haven't already, please select the answer that solves the problem. This will help other users with similar problems find the solution. Thank you for contacting Mozilla Support.

No, It has not solved the problem. After restarting my computer It stopped working again. I tried the firewall again, no luck, uninstalled and reinstalled and restarted my PC. nothing solved the issue.

Use these links to create a new profile. Use this new profile as is. Is the problem still there?

https://support.mozilla.org/en-US/kb/how-run-firefox-when-profile-missing-inaccessible

http://kb.mozillazine.org/Profile_folder_-_Firefox#Navigating_to_the_profile_folder

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

https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles

Type about:profiles<enter> in the address bar.

Use these links to create a new profile. Use this new profile as is. Is the problem still there? https://support.mozilla.org/en-US/kb/how-run-firefox-when-profile-missing-inaccessible http://kb.mozillazine.org/Profile_folder_-_Firefox#Navigating_to_the_profile_folder https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles Type about:profiles<enter> in the address bar.

When I type "about:profiles" it does not load

Hi ecbs5001, did you reinstall the Visual C Runtime files from Microsoft?

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 and 2019":

• https://support.microsoft.com/en-us/help/2977003/the-latest-supported-visual-c-downloads
• https://aka.ms/vs/16/release/vc_redist.x64.exe
• https://aka.ms/vs/16/release/vc_redist.x86.exe

You may not need the latter (32-bit version) if you use 64-bit Firefox. You may have to reboot the computer.

I think there might be a deeper issue here. I tried to install and run waterfox, but it displayed the same symptoms.

That doesn't really answer my question.

I have reinstalled the Visual C Runtime files using the links you provided. I restarted my PC and tried reinstalling Firefox, however I am still getting the same issue. When I have gotten it to work it is always an auto update that breaks it again.

The first screenshot in your original post -- the one with the blank alert box -- is interesting. Are you still getting that empty box?

If you call up the Browser Console using Ctrl+Shift+J, are there any error messages listed?

I do seem to be getting an error message.

win.gBrowser is undefined sounds like a problem, even though it is in the Telemetry module, which is not essential to running Firefox.

In another thread, a user reported that a recent update of Malwarebytes Anti-Exploit (version 415) may be causing symptoms similar to the VC Runtime problem. If you have MBAE, it should have a setting to exempt Firefox. You could test whether that makes any difference.

I made an exception for Firefox, that seemed to do the trick.

Well, once again I am getting the error. This is after unisntalling malware bytes. I am getting the same problems as before.

Have there been any major Windows updates on your system recently, or other software installations or uninstallations?