Hi, try PCs Start button > Restart (do not use Shutdown because in Win10 - by default, Fast Startup is enabled, which doesn't actually shut down the PC)!

Try temporarily disabling Win Defender and any other security software you have on the PC.

Make sure you followed all the steps in performing a Clean reinstall. This means you remove your Firefox program files and then reinstall Firefox. This process does not remove your Firefox profile data (such as bookmarks and passwords), since that information is stored in a different location.

To do a clean reinstall of Firefox:

1. Download the latest Desktop version of Firefox from mozilla.org (or choose the download for your operating system and language from this page) and save the setup file to your computer.
2. After the download finishes, close all Firefox windows (or open the Firefox menu and click the close button ).
3. Delete the Firefox installation folder, which is located in one of these locations, by default:
   • Windows:
     • C:\Program Files\Mozilla Firefox
     • C:\Program Files (x86)\Mozilla Firefox
   • Mac: Delete Firefox from the Applications folder.
   • Linux: If you installed Firefox with the distro-based package manager, you should use the same way to uninstall it - see Install Firefox on Linux. If you downloaded and installed the binary package from the Firefox download page, simply remove the folder firefox in your home directory.
4. Now, go ahead and reinstall Firefox:
   1. Double-click the downloaded installation file and go through the steps of the installation wizard.
   2. Once the wizard is finished, choose to directly open Firefox after clicking the Finish button.

More information about reinstalling Firefox can be found here.

WARNING: Do not use a third party uninstaller as part of this process. Doing so could permanently delete your Firefox profile data, including but not limited to, extensions, cache, cookies, bookmarks, personal settings and saved passwords. These cannot be easily recovered unless they have been backed up to an external device! See Back up and restore information in Firefox profiles.

Please report back to say if this helped you. Thank you!

Thank you very much for the information. I did "clean" install multiple times without success. I run Firefox from command line as "Administrator" and could see blip on task manager for Firefox service and it stops right away. There is something stopping Firefox from executing. As I mentioned, I run standard Microsoft Windows 10 antivirus and standard firewall.

OK, assuming that other browsers/programs run? FF v56.0.1 included a migration for users of 32-bit FF to 64-bit, and there has been isolated instances of issues similar to yours afterwards. So try downloading the 32-bit version from https://www.mozilla.org/en-US/firefox/all/

If this doesn't solve it, and no-one else picks it up, I'll ask in the contributors advanced troubleshooting forum for more ideas.

Scribe said

OK, assuming that other browsers/programs run? FF v56.0.1 included a migration for users of 32-bit FF to 64-bit, and there has been isolated instances of issues similar to yours afterwards. So try downloading the 32-bit version from https://www.mozilla.org/en-US/firefox/all/ If this doesn't solve it, and no-one else picks it up, I'll ask in the contributors advanced troubleshooting forum for more ideas.

So did try you idea and it worked, thanks.

Hello,

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 more easily. Thank you for contacting Mozilla Support.