Look on your desktop. Do you see a folder called; Old Firefox? Look inside. Look for the folder with the latest creation date.

https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile

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

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

What Fred mentioned, with the Old Firefox Data folder sitting on your desktop, is one possibility as what could have happened - Firefox did a Refresh / Reset for some reason - and Firefox automatically created a new Profile when you opened it. https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data But with a Refresh your bookmarks and passwords are supposed to be carried forward to the new Profile. That's why I wonder if you just have a new Profile, with the older Profile still being intact.

You can see if that happened like this: Type about:profiles in the URL bar and hit Enter.

Do you have more than one Profile listed there?

If so, for the Profile immediately above the Profile that shows This is the profile in use ... use the Launch profile in new browser button and then see if your Firefox data is in that Profile.

If that works, close that "new browser" window and go back to the about:profiles page that is still open.

Then use the Set as the default profile button and close Firefox. The next time you open Firefox that Profile will automatically used with a normal launch of Firefox.

Hello folks,

Thanks for our responses. checked about:profiles and it only listed the new default profile. From the other links I found my old profiles and restored them by creating new profiles linked to the saved versions.

Thanks for your help!

I am glad to hear that your problem has been resolved. If you haven't already, please select the answer that solves the problem. This will help other users with similar problems find the solution more easily.

Thank you for contacting Mozilla Support.

I have this problem. I shut down and when I restarted, everything waas gone. A disaster for sure. A lot of stuff Ive saved that gonna take a long time to replace. Why did this happen and how do I fix it?

Have you looked at the postings above?

Fortunately for me, I synced with my phone and got it all back. I would still like to know what happened