The computer going to sleep has been a problem for Firefox for a long time. Best to not let the computer sleep, or shut the browser down when not in use.

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

Type about:profiles<enter> in the address bar. How many profiles are listed? How many should be there? Also, open the profile folder in your file explorer.

https://support.mozilla.org/en-US/kb/recover-user-data-missing-after-firefox-update

Hi FredMcD, I didn't know that, I've been using Firefox for a decade and it never did something like this, but I did as you suggest thou, quit firefox then put the macbook on sleep. Anyway, I've already tried all the links you posted but none of them worked for me (the second one doesn't exist anymore btw, see image), even trough Terminal it still wont open the Profile Manager. It's very frustrating because it just happened without a reason: I didn't cancelled or removed or renamed anything. I can't digit about:profiles either, it does not open and I tried to cancel the file profiles.ini to force it to create a new one but nothing. :(

Also this...but nothing https://www.macupdate.com/app/mac/10700/firefox/uninstall

So my hope is to cancel all about firefox and install it from scratch, I've cancelled the folder in Application Support and the App from Applications's folder, downloaded a new version from the Mozzilla home page and run the installation. I've double clicked on Firefox icon, seen it create a new Firefox's empty folder in Application Support's folder, but after the first check it does after the installation's process, it still doesn't open for the same reason, I get always the same message: profile is missing or not accessible.

How can I get to complete erase Firefox from my MacBook and start again? I can sync it with my iPad and get most of the things back

Thanks again, I hope someone can help me out here.

I called for more help.

thank you very much, I appreciate that :)

Hi FredMcD,

I got it back. It turned out, that my Mac's caches folder was somehow not a folder anymore and as soon as I replaced with a 3 years old backup copy firefox started again to work. Super weird!!! The caches folder under /Library/Caches was a Textedit document. I don't have a clue how did it turn into that but now my problem is solved. thank you anyways

Patrizio

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.

Removed Post

I asked an admin and received this; AliceWyman said

On macOS, Firefox needs a working ~/Library/Caches folder for it to run - see https://support.mozilla.org/en-US/questions/879423 Firefox will not open after fresh install in OSX Lion. "Firefox profile missing." If the Library/Caches folder turned into a text file causing Firefox not to open, that sounds like a macOS bug not a Firefox bug, but you can suggest that the user file a bugzilla report and see what comes up.