2005 aftermarket radio with no sound


I have the Base V-6 and am trying to install an aftermarket double din Bluetooth. Everything seems to work but I cant get any sound at all coming from any of the speakers. I plugged up the factory head back up and they play. There is no factory amp as far as I know. I have the Metra harness so I wouldnt have to cut any wires. Is there something that I am missing? I have the red to red , yellow to yellow, black to black etc...