This is a problem with the profiles.ini file that registers all Firefox profiles. The profile folder is in the ~/Library folder in your home directory and not in the global /Library folder if that is where you are looking.

In Mac OS X v10.7 and later, the ~/Library folder in the Home directory is a hidden folder.

• http://kb.mozillazine.org/Show_hidden_files_and_folders#Mac_OS_X

Make sure that the permissions of this folder are OK.

• https://appletoolbox.com/2016/07/fix-corrupt-user-accounts-macos/

• ~/Library/Application Support/Firefox/Profiles/<profile>/
• ~/Library/Caches/Firefox/Profiles/

You can use the Profile Manager to create a new profile.

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

Thanks I have seen all of the links you suggested. I have completely uninstalled and reinstalled Firefox and all the data about 5 times but I am still getting the "Your Firefox profile cannot be loaded. It may be missing or inaccessible" and am unable to access the profile manager . Any more suggestions?

Reinstalling Firefox won't help, you will have to locate the profiles.ini file.

Did you try to use the Profile Manager to create a new profile?

I have located the profile.ini file.

In terminal I tried to create a new profile using: /Applications/Firefox.app/Contents/MacOS/firefox-bin -P but receive this error in terminal: Error: Access was denied while trying to open files in your profile directory and this error pops up in Freifox: Your Firefox profile cannot be loaded. It may be missing or inaccessible.

You can try to do some maintenance and cleanup with OnyX.

• OnyX: https://www.titanium-software.fr/en/onyx.html

I downloaded onyX and ran the maintenance on my machine - Firefox STILL not working. :(

Can someone please help me with this? I have run onyX and it didn't help.

Problem solved - I reset my user permissions using info from this page: https://appletoolbox.com/2016/07/fix-corrupt-user-accounts-macos/