Radio works but no sound?

[97GMCSierra1500]

I have a 1997 gmc sierra 1500 with a aftermarket radio. I just did a motor swap on it and took it to a shop to finish timing it and before i took it there the radio worked fine but i just picked it up and now i have no sound out of my speakers. The radio turns on and everything works on the screen. I've tried fm channels a cd and a ipod and no sound comes out my speakers on any of those. Im confused if anyone knows what could be wrong i'd really appreciate it. Thanks.