I have Riffstation on my Mac and am very satisfied with it, but the version for the iPhone and iPad are absolutely useless. You must first have an account with, FB, Twitter, Google or log on with you email account. When you get logged in then the problem is you cannot load the songs that you are working on from your iTunes base and when you let the system find the song you cannot open it do to a GEMA conflict.
Either fix it or get rid of it, I have deleted it from my devices.
Mantrailer about Riffstation - Guitar Chords, v1.08