Im not getting any help

ok. my ipod wont play anything i bought from itunes. nothin. everything else works. i buy stuff with 2 accounts, one is mine, and the other is my dads. i dont hace a credit card, so sometimes i use his when my "allowance" runs out. so some things are bought with different accounts from eachother. im just throwing that out there if that might be the problem. please, can someone help me? i have done 2 other posts and i only got 1 reply form an apple employee on both and it still wont let me play them