Hi there, I understand that the email address that you are using to login to your sync account is not recognized. I am sorry to hear that, it sounds frustrating. I am happy to help further after some confirmation of the following troubleshooting steps: #Please confirm that you still have access to the email address being used to attempt your login? #Can you please confirm what version of Firefox you last successfully synced you Firefox profile? # What happens when you try to create an account with that email address? Thank you, and I am looking forward to you getting back to me.