I agree with Sherm that it takes time for the refrigerator to cool. His description of them is spot on; they make no noise. I somewhat disagree with the statement that propane is faster, at least in my Dometic. On 120 vac, it is generally close to operating temperature within 5-6 hours of startup. You need to plug it in at least 12 hours ahead of time (on 120 vac or propane).
Moving the thermistor will do nothing to hasten cooling down. If the refrigerator, when cool, isn’t staying cool enough for your preference, relocating the thermistor from the cooling fins may solve the problem by “confusing” the refrigerator into thinking it isn’t cool enough, thereby applying heat to the refrigerant for longer periods of time. The refrigerant, not being driven by a compressor, circulates only by convection currents, which are caused by heat being applied to the closed system that contains the refrigerant. And the refrigerant is not Freon, it is, from my understanding, ammonia based.
If you start it on 120 vac, be patient. If it doesn’t get cold after 12 hours, try starting it on propane, you may have a problem on the 120 vac side. If it still doesn’t get cold on propane, then something is definitely wrong with the refrigerator. Are you sure the 120 vac breaker is on? These refrigerators require 12 vac to operate, and the lights are likely powered by 12 vdc. Also look in the refrigerator compartment from the outside. The refrigerator should be plugged into an outlet (out of immediate sight) above the hatch opening.
What a long strange trip it’s been!