I had synced my new computer with my old computer and had no problems. My new computer crashed and I had to clear my H on the new machine. When I tried to re-sync the new computer again, it will not work.
when I set up the sync on the new machine, it generates the sync code, I go to sync on the old machine and put in the sync code, it just goes back to the set up sync, pair devices screen and nothing is synced.
I tried to look up my recovery key, but when I go to the sync tab, I don't have a Manage Account tab to click on
Both devices need to be online at the same time if you want to pair a device with the (3x4) 12-character code.
Sync needs to be set up and working on at least one (desktop) computer, so you can enter the 12-character code that is provided by the device (computer) that you want to pair on the computer that has a working Sync setup.
Enter all details like the account name (email address) and password and the 26-character Sync key manually to connect to an existing sync account instead of using the 12-character code to pair a device if pairing isn't possible.
open "Tools > Options > Sync" or "Firefox > Set Up Sync"
click "Set Up Firefox Sync" to go to "Firefox Sync Setup"
click "I Have an Account" : Connect
click "I don't have the device with me" at the bottom to enter the account settings (email, password, sync key)