hello sharmaroushan, firefox 29 and upwards is using a different sync system which isn't compatible with accounts set-up in older versions. in this case you'd probably have to use a workaround and download the prior firefox version, disable automatic updating for the moment (in options > advanced > update), link it to the old sync account and upgrade after you have successfully restored your data this way... [[Install an older version of Firefox]] <br>[[How to update to the new Firefox Sync]]