I've read all the suggestions but can't get Firefox Sync to transfer the open tabs from my old PC to my new one. I'm signed in on both to the same account, both are on my LAN with a wired ethernet connection, and I've checked every box in the "what to sync" field. When I click "Sync Now" the icon spins for a few seconds like it's doing something but the tabs from the old machine do not appear on the new one as I expected them to. Nor can I get them by closing and doing a Restore Session.

This seems pretty straightforward and how most users would expect it to work - am I missing something? If not, why isn't it working?