Please provide some information about how you are using Sync.

Is this issue with a new Firefox installation? Such as with a new device or one that didn't Firefox installed previously. If so, are any other devices connected to that Sync / Firefox Account?

Is this after doing an Operating System re-installation with a fresh installation of Firefox? If so, did you reset the Firefox Account Password before re-connecting to Sync?

the-edmeister said

Please provide some information about how you are using Sync. Is this issue with a new Firefox installation? Such as with a new device or one that didn't Firefox installed previously. If so, are any other devices connected to that Sync / Firefox Account? Is this after doing an Operating System re-installation with a fresh installation of Firefox? If so, did you reset the Firefox Account Password before re-connecting to Sync?

this is after doing an perating system re installation. and i dont reset ff password before connecting to sync.

ali35000 said

this is after doing an perating system re installation. and i dont reset ff password before connecting to sync.

Sync wasn't intended to be used it that manner; i.e., as a backup medium prior to doing an OS re-installation. Sync was intended for synchronizing Firefox user data across multiple devices, where the users data would be present on multiple devices.

Perhaps a Sync error-log was generated when you connected (or tried to) to the Sync service. Type about:sync-log in the URL bar and hit Enter. Were any error logs generated at the date & time you logged into Sync?

YES....