See if anything in this KB article helps you: https://support.mozilla.org/en-US/kb/firefox-sync-troubleshooting-and-tips Knowing the account name (email address) for your Firefox Account doesn't help us help you., but "spiders" harvest email addresses from open forums such as this. You need two things to be able to login to your Firefox Account and connect to the Sync service; your email address for that account ''(which you have)'' and the account Password that was in use the last time one of your Sync connected devices was in contact with the Sync server. That Password is the "key" to unlocking your data and getting connected to the Sync server to retrieve your data; if you change that Password your data is cleared from the Sync server, as that data can't be decrypted without using the correct "key", IOW the original Password. Did you use the correct Password when you connected that new PC to Sync? Or did you '''Reset''' the Password for your Firefox Account?