Sorry that you are having that problem. Typically Sync works, or it doesn't. Nothing the user can do if it doesn't sync to a new device. Any problem with your Password for your Firefox Account, ''that is used by the Sync service'' ? If you requested a new Password while trying to get Sync to work, that is your problem. Your data is gone, wiped from the Sync server. The original Password held the "key" to your data which is encrypted when your data is off your devices. A different Password / "key" couldn't decrypt your data, and thus that data is deleted to allow the user to continue using that account / email address. That feature is also used as a maintenance mode, to allow the user to start with a fresh load of data in cases were the users Sync data is corrupted. ''Prior to Firefox 29 when that feature was added to Sync and "Firefox Account" was coined / created, all the user could do it their data was corrupted was to create a new Sync account using a new email address. I for one went thru 6 different email addresses over the years between Firefox 4.0 and Firefox 28.0. And once Firefox 29 came out I was able to clear that corrupt data and go back to using each of the 5 accounts that had been corrupted. Yes, I did that just to see if it worked for even the oldest accounts; it did work with all.''