I assume you are having a problem with Sync services. Overall, my hunch is that this might be a case of user error or a misunderstanding of how Sync works and how it was intended to be used. Firefox crashing and merely updating your Firefox program installation shouldn't have resulted in you losing your Firefox Profile, which is where your Firefox data is stored. ''Unless you did something that your haven't yet mentioned ...'' As far as Sync goes ... 1. Not sure why you had a problem with logging in to Sync with your Firefox Account, but the action of using the same email address and then setting the password probably cleared your data from the Sync server. ''Changing the password for a Firefox Account also clears all saved data. The password is used to create a "key" which is used to encrypt data as it is sent to the Sync server; a different password would have a different "key" which couldn't decrypt the user's data. So rather than the user needing to create a new Account using a different email address the Sync server is set up to clear the useless data to allow a fresh load of data.'' 2. Sync wasn't intended to be a backup media for a solitary device. If your data isn't on another device, you may be out of luck in recovering your data.