Created attachment 8583286 [details] Screen Shot 2015-03-25 at 12.50.59 PM.png As you can see on the attached screen shot the preferences show that I'm using a Fx Account already for Fx Sync. But somehow I keep getting the yellow warning at the bottom which tells me that I need to upgrade to a Firefox Account?! When I click on the "Upgrade" button in that yellow bar I get to the web page you can see in the screen shot, which is probably false, as firstname.lastname@example.org is already an existing Fx Account (so creating as a new account is foreseeable going to fail). I migrated from an old Sync to the new Fx Account based one some time in 2014 when we introduced the Fx Account based syncing.
Created attachment 8583290 [details] Screen Shot 2015-03-25 at 12.56.42 PM.png Apparently my prediction was wrong: at least according to the screen shot Fx Accounts no longer knows about my account. Did my account got lost? BTW showing that yellow warning to "upgrade", because the Fx Account fails is not very good either.
:drno, Based your screenshots: 1) Your browser is still connected with to "Legacy Sync", not "FxA Sync". 2) There doesn't exist a Firefox Account for email@example.com (Unknown Account error). Some thoughts: 1) Did you use another email? 2) Did you do the upgrade on another machine in 2014? After you upgrade one machine, you still need to log in/upgrade to other machines.
As per comment 2, this is a legacy sync account so the behaviour is as expected.