vu meter problems

ok so my megadrum is all wired up and the lcd works with a good contrast and such. however when i turn it on with no inputs it goes to the megadrum page and then goes to the vu meters. im assuming that is good. however heres where i get annoyed. when i plug in a pad minto one of my inputs and turn megadrum on, it does the exact same thing and even if i hit pads or anything it doesnt change?
what has gone wrong?
what has gone wrong?