TV shows will not sync

I'm trying to sync House of Anubis season 1 episodes 3 and 4 to my iphone but I keep getting an error saying they cannot be synced because they cannot be played on a iphone. Those episodes synced to my ipad just fine and episodes 1 and 2 synced to my iphone fine as well so I don't know why episodes 3 and 4 will not.