https://support.mozilla.org/en-US/questions/1210290) Page Not Found

Did you post the correct link?

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}

Very sorry, but I had an extra parenthesis in the URL. The correct one is the following: https://support.mozilla.org/en-US/questions/1210290

The problem remained after I turned off firewall. I forgot to mention that I restarted the computer all all the cleaning, and ran Firefox in the regular way and as an administrator to no avail.

It is strongly recommended that you never mess around in the Windows registry. Things like this are exactly the reason why. Things can potentially break, and there is no real clue as to what is wrong.

Please uninstall Firefox using the Windows Control Panel, then download it from www.getfirefox.com, and try installing again.

Do you use "Registry Cleaners" or any other such junk products on your computer? If so, please remove them.

I did it out of desperation. It has been more than half a year since Firefox stopped running. As you can see from the archived thread, I tried all kinds of recommended remedies. I did not use any tool to clean the registry this time. I just ran regedit, and search for every entry containing "firefox", then delete it one by one.

It definitely sounds like your Windows install is corrupted. Try the steps at https://answers.microsoft.com/en-us/windows/forum/windows_10-update/system-file-check-sfc-scan-and-repair-system-files/ to try a repair.

Since the page(https://answers.microsoft.com/en-us/windows/forum/windows_10-update/system-file-check-sfc-scan-and-repair-system-files/) shows "Page Not Found", I used the following:

https://support.microsoft.com/en-us/help/929833/use-the-system-file-checker-tool-to-repair-missing-or-corrupted-system

I got the following:

C:\WINDOWS\system32>sfc /scannow Beginning system scan. This process will take some time. Beginning verification phase of system scan. Verification 100% complete. Windows Resource Protection did not find any integrity violations.

I have already wasted a lot of time on this, and I hate to waste others' time on this any more. I will just wait till I get a new computer in a few months and try it again.

Can you open the Profile Manager to create a new profile?

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

It is possible that your firewall or other security software blocks or restricts Firefox without informing you, possibly after detecting changes (update) to the Firefox application. Remove all rules for Firefox from the permissions list in the firewall and let your firewall ask again for permission to get full, unrestricted, access for Firefox and the plugin-container process and the updater process. See:

• https://support.mozilla.org/en-US/kb/server-not-found-connection-problem
• https://support.mozilla.org/en-US/kb/Firewalls
• https://support.mozilla.org/en-US/kb/fix-problems-connecting-websites-after-updating

Boot the computer in Windows Safe mode with network support to see if that has effect in case security software is causing problems.

• http://www.bleepingcomputer.com/tutorials/how-to-start-windows-in-safe-mode/
• http://www.7tutorials.com/4-ways-boot-safe-mode-windows-10

I am unable to start the profile manage. Tried every way. I have tried disabling Firewall many times to no avail. I have just tried Windows Safe mode with network support again to no avail. This stubborn problem does not deserve anyone's time anymore.

Did you do a clean reinstall and delete or rename the Firefox program folder?

Yes as far as I know . The following is from my initial post:

1. . Uninstalled Firefox.
2. . Deleted Firefox folders under both AppData\Local and AppData\Roaming
3. . Deleted Firefox folders under Program Files
4. . Searched and deleted every entry with word "Firefox". This took over an hour. The registry was completely free of "Firefox"
5. . Downloaded and installed Firefox.

Hallelujah!!!

I have finally been able to use Firefox with the same remedy that I have just used the solve the same problem with Thunderbird - using an older version. For Firefox, I have to go back many versions to the last version of Firefox 58:

Please update to Firefox 63 now, glad you got it working?

Sorry for not making it clear in my excitement. The newer versions (versions after 58) do not work on my computer, and this is exactly the reason I went back to 58. I tried all of the newer versions to no avail.

Did you try 32-bit Firefox versions?

• https://www.mozilla.org/en-US/firefox/all/

The 32-bit version was the first thing that I tried, but it did not make any difference.

I do not know what is responsible for this problem - Firefox or Windows 10. On the one hand, I seem to be the only person reporting this weird issue. On the other hand, Mozilla apps (Firefox and Thunderbird) are the only ones with this strange problem. I have over 100 applications running on this Windows 10 PC without this problem.

Now, I can confidently declare that I am able to use the latest version of Firefox finally. Summary of a long story:

1. I upgraded the hardware of my PC (CPU, RAM and motherboard) last December, but used the same Windows 10 installation initially. The problem remained.
2. I did a clean install of Windows 10 (i.e. on a brand new SSD with new partitions) in late January, and I have been able to use the latest Firefox without any problem since then.

This has also solved the similar problem of not being able to run the latest version of Thunderbird. The old Windows 10 installation is a result of multiple OS upgrades starting from Windows 8.0 or Windows 7 (it went through all versions of Windows 8 and Windows 8.1). I think it must be some residue from those upgrades preventing the use of the latest version of TB or FF.

That was very good work. Well done.

Sometimes an update on top of an update on top of . . . . . can cause issues. That is why sometimes when a program is not working properly, we sometimes tell them to do a clean reinstall with the current installer.

It is very challenging for me to reinstall all the programs some of which require dealing with license issues. I did the clean installation late January and expected to migrate all the apps by the end of February. Unfortunately, I still have about 20% to go by now (middle of March). I have kept the original SSD with the old installation (as Drive O) ready for me to boot the computer from. I still boot from it occasionally in order to use programs that have yet been migrated. I have moved the target date to the end of April.