R4DS Revolution

Hello i have a r4 and 2 sd cards ,santa brought them for my son !!!!. which came already sorted. i have loaded a few games on each all was fine then one of the cards would not load, just gets stuck on `loading` checked on pc and the files would not show up but in properties it said they where there (due to free space/ space used ).
Then next it said this volume needs formating and would not let me access it, so i did and downloaded the files as described got the four files
_system_ , _ds_menu ect..... put them on the card but still the same can anybody help please

Thank you