The refrigerator will run on 120 volts and 12 volts, or it will run on 12 volts and LP gas. Be sure your coach (house) batteries are fully charged. Be sure you have LP gas flowing. Light all of the burners on the kitchen stove first to get the LP gas flowing closer to the refrigerator before trying the refrigerator on LP again.
Your red indicator for "lp on" may be telling you that you do not have 12 volts from your coach (house) batteries, it could be a fuse, or it could be the red indicator bulb burned out. I've replaced that bulb twice in 10 years.
Regarding your statement I also read the manual for 2 AC units and it says to turn on both AC units simultaneously push the mode and fan button to show both units on the controller it didn't work. Any help will be greatly appreciated.
Regarding the 2 ac units. Does the face of your thermostat illuminate when you push the button(s)? If yes, you have 12 volts to the thermostat. If no, then find out why you don't have 12 volts to the thermostat.
Your front a/c is zone 1, and the rear a/c is zone 2. To switch between zones, depress the top two buttons on the 4 button thermostat at the same time and release. This should change the indicator on the thermostat from zone 1 to zone 2 (or the reverse if you were on zone 2). If this does not work, you may have dirty contacts on the push button switches. The link below is to a thread about cleaning and repairing the thermostat.
link cleaning contacts/thermostat repairFred