https://support.mozilla.org/en-US/kb/how-run-firefox-when-profile-missing-inaccessible

http://kb.mozillazine.org/Profile_folder_-_Firefox#Navigating_to_the_profile_folder

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

https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles

Thanks FredMcD. I already read those articles before I posted. My problem is that Firefox is not creating a profile when I install it (there is no Profiles folder in the "Library/Application Support/Firefox/" folder and I assume one should be created with a new install). This also means I can't run Profiles Manager to create a profile manually (In the Terminal application, when I enter "/Applications/Firefox.app/Contents/MacOS/firefox-bin -P" I get the message "Your Firefox profile cannot be loaded. It may be missing or inaccessible." No kidding. That's the problem I'm trying to solve. Is there a way to manually create a profile? I tried copying an old Profiles folder into the Applications Support folder but still get the message "Profile Missing Firefox profile cannot be loaded. It may be missing or inaccessible" when trying to run the application. Lew

This is a problem with profiles.ini that stores the profile registration.

You can try these steps to make Firefox create a new profile:

• delete the profiles.ini file to make Firefox create a new (default) profile
• use the Profile Manager to create a new profile
  https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles
• register an orphaned profile that isn't listed in the Profile Manager

You can find the profiles.ini file in a hidden location:

• Mac: ~/Library/Application Support/Firefox/

You can recover a unregistered profile via these steps:

• use the Profile Manager to create a new profile
  https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles
• click "Choose Folder" in the Profile Manager
• browse to the location of this profile to register this profile in the Profile Manager and use this profile

See "Profile was moved or renamed":

• https://support.mozilla.org/en-US/kb/how-run-firefox-when-profile-missing-inaccessible

Note you should never use "Choose Folder" to specify a folder that already contains files and that isn't a Firefox profile folder. Only use "Choose Folder" to recover an profile that isn't listed in the Profile Manager.

If this didn't work then check the read/write permissions and ownership of files and folders in both main/root and cache locations and possibly remove the Mozilla/Firefox folder.

Hi Cor-el. You have sent me links to these articles before. Unfortunately, none of these solutions has worked. I think there may be a problem with my user account, and it has been corrupted in some way. I experimented by creating a new admin-level user account for troubleshooting purposes and Firefox runs fine there.

There appears to be no way for me to manually create a profile. As noted earlier, profile manager will not run. I renamed my "profiles.ini" file "profiles.iniOLD" as suggested in the "How to run Firefox when Profile Missing or Inaccessible" article, which says that a new profile will be created when re-starting Firefox, and a new profile is not created. (I still get the same "Profile Missing Firefox profile cannot be loaded. It may be missing or inaccessible.").

I have been dead in the water now for over two weeks. I backed up my entire hard drive about a month ago. I wonder if copying the profiles folder from a backup file would work? In any case, all of my research, my bookmarks (thousands) and website passwords etc. are in my profile folder and I have been unable to do any work. I don't think my college IT department will be able to help with this problem. I need to hire someone who knows Firefox, and MacOS. Any recommendations?

You can try to do some maintenance.

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

I was able to fix the problem by going the ~/Library/Caches folder and deleting the entire contents of the folder (make a backup first). I restarted the computer and Firefox was then able to run again as a new install but missing all bookmarks, passwords, history etc. as I had already removed my existing/previous Firefox Profiles folder when (unsuccessfully) attempting to get Firefox to run after a reinstall.

I again tried replacing the entire Firefox Profiles subfolder (not sure what it is called, but it has a ".default" extension) with my old subfolder, but when I tried to restart Firefox I got the old "missing profile" message. I then removed the old folder, put the new folder back, and went in and replace the following files only:

• places.sqlite (bookmarks, downloads and browsing history)
• favicons.sqlite (website favicon images)
• key4.db (key database for passwords)
• logins.json (encrypted information about saved usernames and passwords)

I crossed my fingers and Firefox was able to restart this time and my bookmarks and saved passwords all seem to be working fine. There must have been a problem with my MacOS user account profile. Really quite unbelievable how difficult this was to diagnose and fix. Thanks @core-el and @FredMcD for the links and suggestions.

Running OS 12.3.1

That was very good work. Well Done. Please flag your last post as Solved Problem as this can help others with similar problems. Go to that post and click the 'Solved' button to its right.