First, press the back up release on the back of the bar if the door does not release the there is a fault in the systems general wiring. Check the system wiring.
Second, if the door does release when you press the back up release button check the sensitivity adjustment potentiometer on the back of the board turning the POT clockwise will increase the sensitivity and the bar may begin to function.
Third, if the door does release when you press the back up release button and you have tried adjusting the sensitivity then you need to check the voltage for the bar at the six pin connector that connects the cable to the board. Checking between red and black with a meter you should see system voltage.
Fourth, if the back up button works, you have tried adjusting the sensitivity and you have good voltage at the six pin connector check the antenna wire and make sure it is connected to the bar via the Phillips head mounting screw also check to make sure that the screw is not stripped. Meter between the face of the bar and the point were the antenna wire solders to the board you should see near zero resistance.
If everything checks out contact the factory.