I had the same after installing an aftermarket radio. In my case I just pulled off the dash again, re-plugged all electrical connectors and put it back, everything was working ok. It seemed to be a loose connection in the wiring.
I suggest trying that, it is easy to grip the two vents and pull the top of the panel out to check the connectors.

 

That's good advice, prod. Pull that waterfall off, take the radio out, and have a look. Who knows, maybe previous owner meant to say, that it actually was an aftermarket anti-theft device(or ??) that was installed. Look for anything out-of-place, anything that looks not original.