Cadillac: 1996 eldo wont start after stereo installed, cadillac elderado, car stereo installation

Question
i have a 1996 cadillac elderado and i took it to a car stereo installation place. i had them install a stereo system and the stereo sounds great. but they called me right after the stereo was installed and they said that the car wont turn over, but the dash light and the radio lights come on. i dont know if this a electrical problem or not but i have never had a problem with the car not starting. its always turned over on the first try. they checked everything they went over and couldnt find nothing. plz help i dont know what to do.

Answer
If you drove it in and it worked OK, Then it is most likely that they did not install the stereo correctly and the ignition is now locked out.

Have them re-install the original radio and see if it starts. If it does NOT, Then there is a wiring short somewhere in the radio system that connects to the ignition lock-out .