Is this a case of you do not intend using the email account in the future or are you unable to use it for some reason ? Or are you ssying Sync has stopped working ? Have you still got access to and are able to us that email account ? See *[[I've lost my Firefox Sync account information - What to do]] * [[How do I set up Sync on my computer?]] *[[Firefox Sync troubleshooting and tips]] If possible you should ensure the devices are synced then set up Sync again with the new email account. Note Sync is NOT intended to be a backup service. Your own synced devices are the backup.

Can you connect to the account here: *https://accounts.firefox.com/settings