What about the rest of your profile? Settings, bookmarks, history, passwords . . . .

Sometimes when the browser thinks there is a problem with the profile, it will create a new one.

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

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

No, this didn't help me get the tabs I had open. I never had this problem with Firefox until the last update. I hate to say this, but you ruined weeks of work, I will never use this browser again, and I'm back to Chrome. Chrome failed me like Mozilla Firefox. at least it's dependable.