VDX 404

VDX 404
WHAT WORK YESTERDAY DOES NOT WORK TODAY. NO REAR CAMERA ONLY LEFT AND RIGHT CAMERA VIEWS.
WITH SOME WIRE SWITCHING I HAVE A REAR CAMERA THAT IS WORKING BUT DOES NOT GET THROUGH THE VDX 404 SYSTEM. I SWITCHED THE DRIVERS SIDE CAMERA OUTPUT #2, AND PLUGGED IN THE REAR CAMERA OUTPUT TO SEE THE REAR. CAN THIS VIDEO SWITCH LOOSE IT'S PROGRAMING MEMORY? CAN IT BE RESET? HOW TO TROUBLE SHOOT IT WITHOUT A PC CONNECTION?
IT HAS WORKED FOR 7 YEARS. DID IT DIE OR COULD IT BE FIXED?