HI swight,

I understand that Firefox will not open. The question is in the Firefox for Android section, so I will change this to the proper install of question. I might recommend to try a clean reinstall: 

Certain Firefox problems can be solved by 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, please follow these steps: Note: You might want to print these steps or view them in another browser.

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.

Start Firefox in Safe Mode {web Link} by holding down the <Shift>
(Mac Options) key, and then starting Firefox. Is the problem still there?

It is possible that your firewall or other security software blocks or restricts Firefox or the plugin-container process without informing you, possibly after detecting changes (update) to the Firefox program.

Remove all rules for Firefox and the plugin-container from the permissions list in the firewall and let your firewall ask again for permission to get full, unrestricted, access to install for Firefox and the plugin-container process and the updater process.

See:

• https://support.mozilla.org/kb/Server+not+found
• https://support.mozilla.org/kb/Firewalls

• https://support.mozilla.org/kb/fix-problems-connecting-websites-after-updating

Thank you for trying to help.

1. I tried to do a clean reinstall of Firefox as suggested above but don't know which of the Firefox folders to delete as none are labelled installation folder. 2. This is a PC and the shift option to open Firefox in safe mode does not work. 3. Before posting here I had tried to find out if the firewall was preventing Firefox from opening but there is no list there of prevented connections. I don't want to turn it off altogether. The box 'Block all incoming connections, including those in the list of allowed applications' is not ticked.

I appreciate you all taking the time to try to help.

Regards, Susannah

Do Not turn off the firewall. Open it's setting. Go to the page that allows or blocks programs (sometimes call "rules"). Remove ALL of these entries. Most firewalls will re-include safe programs. If something is blocked still, just change it's rule.

Thank you FredMcD. I just did this, deleted all the in rules and all the out rules. Restarted PC, but Mozilla Firefox will still not open. Thanks for trying though. I am getting used to the idea that I will have to stick with Google Chrome, but I miss some of the features of Firefox.