You most likely have a Dometic CCC (thermostat). This is from the manual:
"When your unit was installed the appropriate dip switches on the electronic control
board were turned on to match your system configuration. Any time these settings
are changed, a system reset will need to be done before the CCC 2 thermostat will
recognize the updated selection. To do a system reset:
• Make sure the CCC 2 thermostat is in the OFF mode.
• Simultaneously press the MODE and ZONE buttons. The LCD will display
“IniT” and all available zones.
• Release the MODE and ZONE buttons.
• Press the ON/OFF button to exit system set up."
The CCC sometimes gets a case of amnesia usually if 12V
is interrupted for some reason, maybe for other unknown reasons that seem to cause glitches in a lot of our high tech gadgets. The reset often puts everything straight again.
If this doesn't fix it, it might be time to call or take it to the dealer. As mentioned above, the switches on the control board may not have been set correctly assuming this has never worked or the board may be kaput.