No sound from factory radio
 

I have a 1999 GMC Yukon (Stereo Model # 16265885). I recently installed the factory radio after having an aftermarket unit installed. The aftermarket unit worked fine but when I installed the factory unit, it does not produce sound. The display works, the CD player works, and I'm able to tune the stations but no sound comes from any speakers.

Not sure if this is related, but the display goes completely black when I turn on the headlights (park lights as well).

Any help is appreciated.

When you installed the aftermarket stereo, did you have to bypass the factory Amp? And if so, did u un-bypass it when installing factory stereo?
I don't know a lot about it, just my experience installing an aftermarket. We had hell lol