My Mac Won't Play New Tracks

[ninjap9]

My Mac book that I got from school has used spotify jsut fine until recently. I can play all my old songs but new songs I want to play don't work and they will not play. What do I do to get them to play. It says that they are playing but no progress is being made and skipping to the middle won't help either. Sorry for the bad grammar I am tired and young.