FYI. Sync isn't a backup system-sync is to sync between device to sync server back to another device. if you reinstalled Windows and Firefox and logged into sync any data that was there before is replace with the new data that doesn't contain the old data. What you need to do was use Firefox FAQ on how to backup the data, profile, login/pswd, and history to restore them back to Firefox. If this wasn't done then there nothing any users on here can do to help.

Hey there ik about that but the thing is my data always comes back when I reset and login I had it backed up but it won't restore it

And also in the forum it says that it auto saves the data even that data won't auto recover

Hi

Did you by any chance use the "lost password" process?