No sound through speakers

[Pat1USMC]

Well I’m at a loss. I have a 1998 Boxster. I thought I had made the headunit swap as easy as it could be. I literally only swapped one aftermarket Alpine headunit for another! Same harness, same 4 RCA plugs, same radio antenna. The headunit powers and works just fine, but there is zero sound coming through the speakers!

I have never had a problem with the first headunit (just wanted Bluetooth capability). It appears to be wired professionally for the first aftermarket Alpine unit but that was with the PO.

This is what I have done for troubleshooting:
-check and replace fuses for stereo and sound. They weren’t blown I just wanted to cover all my bases
-replace stock amp
- disconnect/reconnect negative battery terminal
- the open the drivers door, lock the car, close the door procedure
-drove the car and shut it down. Twice.
-I even put the 1st headunit back in! Still no sound.

Is there something I’m missing that Porsche has installed to prevent headunit removal? This is driving me nuts!