Car Stereo all installed but no sound
 

So I have a customautosound USA-630 Head Unit that I installed in my 71 Chevy Truck. Everything is hooked up properly, unit comes on all functions work, but does not produce sound. Speakers work -tested them when I adjusted my Orion Amplifier. Get sound when I do the gain adjustment all all that, but nothing from the head unit.. Any suggestions?

Okay just thought I would share with everyone that I found the problem! Turns out it was something very simple, usually is, but one of my speakers was grounded which the stereo stops functioning properly to protect itself so I fixed that and I have sound