Audio Systems: Kenwood Car Stereo no display or output, aftermarket stereo, title and registration

Question
Hi Garry
My car came back from it's MOT and the stereo was not working. The garage have no idea what they've done.
There is power to the unit, but no display or sound. I've tried the reset button and the mask key neither worked. I've even changed the battery in the mask key and disconnected and reconnected the car battery.
Do you have any other suggestions to save me from another day of singing to myself?
Many thanks
Christine  

Answer
greetings!! with the limited info you gave me, there's two things right off...both in the same area, if it's the stereo that came with the car, they probably tripped the anti theft circuitry, and you'll need to go to your make car dealer with proof of ownership, maybe title and registration so they can give you the reset code. if it's an aftermarket stereo, the same applies, but you'll have to contact kenwood, or an authorized kenwood autosound dealer/servicer and after proving it's yours, they'll give you the code...be sure to have model number, if at all possible, but i think kenwood has model number on faceplate....good luck....