It must be a simple power or connection issue. I was thinking maybe part of the rig has a wire connection at the battery terminals and that may have loosened or not be connected when the batteries were removed. A beeping LP alarm usually means a lack of 12v power. It's also possible that the converter is not supplying power to the different 12v circuits and that the lights and various 12v devices are getting just enough power from the truck connection. I would definitely replace the batteries and see what happens. Do you have a meter so that you can troubleshoot the electrical system, should that be necessary?
