Most likely, one of the safety features has been activated on the system. This safety feature shuts down the system for 20 minutes to reset itself. Unplug the control head. You will need to disengage the J-arm that connects the motor by removing one of the pins on either end of the J-arm (this will release the pressure on the motor). Next, pull the release cord and disengage the motor from the track. Now reconnect the J-arm and manually close the doors. Pull the cord again to re-engage the motor. Wait until the lights become visible again on the control head. Your system is now ready to operate. If this happened the first time you operated the system, you likely did not set the limit stops or set them in the wrong spots.