Disklavier

hi again,
i managed to get my floppys formatted to the correct type for this RF PPC3 player, i have downloaded a good few songs that work in the player,  some say  midi file after the title and some say .fil       however now the strange thing, a lot of the songs i dowloaded wont play  no idea why! on the screen it says i must register the disk,  i do that and then it sits on a blank screen with no.1 showing but no title comes up and no music seems to be on the disk  although i put it on.