How do I recover an old sync???
I had several tabs from device 1 that were synced on device 2. I went on with life for a few days, but I came back to FF on device 2 today and attempted access my old tabs and everything was gone. This wouldn't be a huge deal if I hadn't already reformatted device 1, so obviously now I can't go back there to get the old tabs. I didn't mess with any of the sync settings on either device, nor did I delete any tabs on device 1 since the last good sync I saw. In fact device 1 was either powered off or not connected to the internet after I synced my tabs.
All I want to know is if there are sync backups that an be accessed online somehow - I'm extremely unhappy about losing the synced tabs but I'm willing to overlook that if I can get them all back.
Opaite Mbohovái (4)
Sorry, there is only one version of data saved by Sync. There is no "old data" point to recover 'saved' data from. IOW, there are no "backups" saved.
Well that sucks. So I'm supposed to just accept that Firefox dumped all of my tabs and move on with life?
Tab history is transitory, it's not saved forever. Typically once another session is started the tabs saved in session history are replaced with the new session when Firefox is closed. Then that data is sent to Sync as "Synced Tabs" for the other devices to use when they connect to Sync
Short version, use 'em or lose 'em - Sync constantly updates data, upon closing and opening, and sometimes during a session. Next session they may be gone.
For what so are posting about I recommend using a Session Manager extension, one that is fully compatible with the new Synced Tabs feature that came in Firefox 47. Session Manager extension search at AMO
Or use Bookmark All Tabs in the contextual menu for Tabs, before you close Firefox on the device that you want the tabs sent to Sync from. That will save those tabs, in one folder that you can label, in your bookmarks until you use those tabs in the other device. Then simply delete that folder in your bookmarks.
Note that tabs from other devices expire automatically after some time (e.g. a week), so you can't keep them forever.