Dont know if this will help or not, but giving it a try wont hurt, we had the same sort of problem earlier on this week with our domestic fridge, i thought it was knackered, but only being two years old, i had my doubts.
power ok to fridge, turned the thermostat up to full and nothing happened, and after two days of milk to yoghurt syndrome, i decided to have a look at the motor to see if anything obvious had happened, loose wire or no gas etc. couldn't see anything out of place, so did the old kick it and see, so i tapped the round tank a couple of times with my foot( steel toe caps), and the motor burst into life, and has been ok ever since...
so just check it isn't stuck in a dormant phase, and the power and thermostat aren't enough to restart it...
The ISOtherm has as far as I know a Danfoss compressor.
The Danfoss has a microprocessor and checks the supply voltage by short current pulse, just a few microseconds. If you have a bad connection from your battery to the fridge it believes that the battery is almost empty and therefore it doesn’t start in order to protect you batteries for deep discharge.
Use a heavy cable direct from you battery to the fridge to diagnose the problem. You won’t see the drop with a normal meter (just a few microseconds’).
or, get a high wattage lamp ( car headlamp bulb) and stick it across the supply at the input to the pump ( top two spades,I think) If you get a nice bright light and still measure a good voltage (over 11, at the pump) then your power to the unit is OK, and we're back to the hammer....ask youself - Did it show any signs of erraticism before finally dying , was it getting noisy -clattering pumps are near the end of their useful lives. was it cooling OK, did it run for longer per day than when new etc.