hello, you could try this "hack" to get a new firefox version to connect to an old sync account: 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. if this worked and you could import your data successfully, please migrate to the new sync afterwards: [[How to update to the new Firefox Sync]]