Spotify Mobile

I'm asked to log-in to my account, so I use my facebook log-in to get in. This works fine and I can see my playlists for a split second. Then, it comes up with a pop-up saying "Discover great music with your friends" and the options are "Have your Spotify details? Please login." or "'I'm new to Spotify! Let's go!".

So I click to log-in as an existing user and then type in the same details and it says "Invalid Username or Password". How does that make sense?! I can't get onto my playlists without going through this process, so I'm stuck. 

Some please help. I'm paying for Premium just to use it on my mobile. So, currently I'm getting no benefits for my £9.99.