hi smash100, firefox 29 and above use a new sync login system which isn't compatible with the old username/password/sync-key method anymore. you could try this "hack" to get a new firefox version to connect to an old sync account though:

enter about:config into the firefox address bar (confirm the info message in case it shows up), right-click somewhere in that page & create a new string preference named services.sync.username with a value like fake. afterwards you should be able to connect to the old account through the firefox options > sync panel. click on set up firefox sync > i have an account > i don't have the device with me where you can enter your existing credentials.

if this worked and you could import your data successfully, please migrate to the new sync afterwards: Sync your Firefox bookmarks, history, passwords and more

Thanks for quick response

I added a string 'services.sync.username' / Value:fake, the rest of your instructions didn't follow:

The options I see are 1) Pair a device > I don't have the device with me > (gives me a recovery key: print/save) but not sure what to do with this? 2) Unlink this device > (goes back to manage screen without the Pair a device option)

Any ideas? Thanks

afterwards you should be able to connect to the old account through the firefox options > sync panel. click on set up firefox sync > i have an account > i don't have the device with me where you can enter your existing credentials.

hi ok, this sounds as if you have already set up the new sync on the new device. in this case please go to "Unlink this device" and start the steps from my prior posting again (starting with the about:config change)...

Thanks - only, there's no option to Unlink device. Only 'Disconnect'. If I do that, then follow your instructions then it's the same story as I described above. It does say 'Firefox Sync will start momentarily' but nothing happens...!

can you please add a screenshot of the sync-tab in the options panel. maybe this can help us to understand the issue better...

Here...

ok, this means that you are connected to a "new" firefox account at the moment.

please click on "disconnect" and restart firefox once. then the interface when you go into options sync should look like in the first screenshot.

in this stage it won't work to reconnect to your old account with your old sync data yet. you then have to perform the hack in about:config described in my first post. then the interface of options > sync will change like shown in the second screenshot.

now you can reconnect to your old sync account: click on set up firefox sync > i have an account > i don't have the device with me where you can enter your existing credentials (note that you need all pieces of information from your old account: username, password and sync key).

Thanks - but how do I get my Sync key? can I retrieve it by logging into the old sync? (can;t see a way to do so)

the sync key should have popped up during the initial setup procedure on your old device with instructions to write it down for future reference. if you don't have it handy anymore then i fear there is no way to get to your old stored data, since it is the only cryptographic key to the data on the sync servers...

Not that I recall. But I swear I saw it at some point in the new version during the steps above....

i'm afraid there is no way retrieving it when don't have access to your old device where old sync was set-up anymore :-/