Old Sync: To add a device to the older Firefox sync, I had to type in a code in the new device's Firefox which was shown in the old device's Firefox. New Sync: To add a new device to the new Firefox sync, I had to just log into my Firefox account on the new device and the FF installation would download all data from Mozilla's servers. All data is present on their servers and is encrypted. So its safe too. My problem: I had been using Chrome at first but then i switched to FFox for the last 3-4 years. All of my chrome and FFox bookmarks of the last 5 years are/were on Firefox. It was fully updated and with the new accounts-based Firefox Sync on Windows 10. I switched to Ubuntu and i tried Chrome for the last 4 months and now I want to move back to Firefox. I installed Firefox and I logged in to my Firefox account successfully without any password reset. But the bookmarks won't sync at all. Questions: Why is this happening? Isn't everything that i chose to sync stored on Mozilla's servers? Is there a way to check if any bookmarks(or any other data) are present on Mozilla's servers? P.S.: My friend did the exact same thing (moved from Win to Linux and logged into Firefox account) and all of his FFox data was synced but its not working for me. Are the FFox data deleted from Mozilla's servers if there's no activity for 4-5 months?