If it works on AC then it has 12VDC ...for display, interior light, controls and propane system
Doesn't work on propane.....
Could be several items. Details would be helpful
Model of Norcold
Has it been a while since you tried propane....might take several attempts to get gas flow
Does it SPARK
Does Flame light and then go out
Does flame light, stay lit but fridge doesn't cool/gets warm
Details cause it could be something simple/cheap or more expensive