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}

Start Firefox in Safe Mode {web link} by holding down the <Shift> (Mac=Options) key, and then starting Firefox.

A small dialog should appear. Click Start In Safe Mode (not Refresh). Is the problem still there?

When I checked my Firewall settings, Firefox wasn't part of the list 'allow incoming connections'. I added Firefox to this list, and when I started Firefox in safe mode, it worked.

However, when I then shut down Firefox and I try to start it in regular mode, it again doesn't load anything.

Try FF in Safe Mode again.

Open the firewall settings and totally remove Firefox.

Try to reset (power on/off) the router.

Try to disable IPv6 (check for other possible causes as well).

• https://support.mozilla.org/en-US/kb/firefox-cant-load-websites-other-browsers-can

I reset the browser and disabled IPv6, but the problems remain. Therefore I enabled IPv6 again.

Also I opened the Firewall settings, removed Firefox from the list, uninstalled and installed Firefox, and the problem remained. I then added Firefox to the Firewall list again, but still the problems remain.

Try to do a clean reinstall and drag the current Firefox installation to the Trash (you probably did this already).

You can find the full version of the current Firefox release (54.0.1) in all languages and all operating systems here:

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

Create a new profile to test if your current profile is causing the problem.

See "Creating a profile":

• https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles
• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Profile_issues

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.

• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox

Try to boot the computer in Mac Safe Mode

• http://support.apple.com/kb/HT1455

I uninstalled and reinstalled Firefox, deleted my current default profile entirely. It means I've lost all the bookmarks etc. but at least that way I was sure that I wouldn't import corrupted files again.

Firefox now work again. Thanks for your help!

Firefox comes in two or more folders on all computers. They are;

Maintenance: (Programs Folder) <Windows Only> Firefox itself: (Programs Folder) And at least one folder in the profile of each user on the computer.

If you remove the Firefox folder, the user folders would not be affected.