mp4 wont play on my galaxy note 10.1

[Vicki Hassall1]

Hi, I'm new to this and I'm hoping someone can help me as I'm ready to scream.. Anyway, I cant get mp4 to play on my note 10.1!! I've tried mx player, dice player vcl or what ever its called. You name it, I've tried it! I have coverted to mp4, ive downloaded mp4, I've updated to 4.1.2..I've even done a factory reset!! No joy. I would presume there is a fault or something but the Harry effin Potter will play, but nothing else will, I don't get it? Any advice would really be appreciated..Thanks :-$