''atulmittal0109 [[#question-1087274|said]]'' <blockquote> I installed an older version of Firefox and when tried to sync, it was asking for sync key. I accidentally changed the key and sync failed. I then, updated to the latest Firefox version and tries to sync again. Sync is working properly but there is no any data to sync. There were many bookmarks, passwords and other data in my old FF profile but I guess, they are lost now. ANy way to recover them back? </blockquote> hello and so sorry to hear about the issue you are having. If you are using a new sync account now (FF 29>) in the new installation and had older sync installed in your windows machine then you need to install old Firefox again to sync. Also do note that sync requires you to keep both of the machine turned on at the same time. If you have your [https://support.mozilla.org/en-US/kb/how-do-i-manage-my-firefox-sync-account?esab=a&s=recovery+key&r=1&as=s#w_where-can-i-find-my-recovery-key recovery key] then you can use that to pull down the information from Sync and get it onto your new machine. Also note you can't Sync between devices with the new Sync version and the old Sync version. You will have to update all devices to Firefox 29 or later to be able to use the new Sync, so you need to install a beta or Aurora Firefox version on the Android device as well. * https://support.mozilla.org/kb/how-to-update-to-the-new-firefox-sync * https://wiki.mozilla.org/Identity/Firefox-Accounts * https://blog.mozilla.org/services/2014/02/07/a-better-firefox-sync/