I've recently noticed that despite sync working on my desktop-laptop-phone there are devices missing when I go to https://accounts.firefox.com/settings * 1. when I visit * on desktop - the laptop is missing 2. when I visit * on laptop - the desktop is missing 3. when I visit * on either of the devices - my smartphone is always there correctly on the list All of the devices have unique names. They ware synced recently and I even tried forcing a refresh by changing their respective names. Also note that that sync works without a hiccup and it works fast. Sending tabs between devices also works, limited to the visible devices of course. Firefox latest stable Windows 10