I presume the fridge works properly on LP and 110/Shore power. It is difficult to determine what hot means to accurately  work out if it is hot enough. The principal of operation is the heating of the Boiler portion high enough to boil and separate the different chemicals inside the system, It can be hot to touch yet not make high enough temperature to boil . Actual voltage measured with a meter will be needed . Was it connected to the tow vehicle and a good charge wire  while on the 12 volt. or just on the trailer/house battery and was that well charged.  You will need at least 12 volts and maybe more to heat  properly. We see 13.2 + while attached to a running vehicle at the fridge supply screws. I hope someone else here can do a better explanation then I can. Sorry.