I've been pulling my hair out over this for an hour. Thanks for the fix. It's absurd that Spotify isn't more clear on that as so many sites ask for username when almost all are an email address. Should fix this.
So I sent an email a few days back about someone else using my account and how I wanted a solution to getting the unknown user off my account. I think someone from Spotify came to my help but now I can't log back in with facebook where my account is premium. If I log in using a username and password (not thru fb) then I just have a free account and none of my playlists are there. Now, every time I try to log back in thru facebook, it says my username and/or password is incorrect and it won't let me get in. I logged out of all devices via fb and tried to re enter my fb info and log in and still the same Spotify message saying my username and/or password is incorrect comes up. So now I have a premium account I pay for that I can't access because I can't get on via fb anymore.