Dometic gas absorption refrigerator are gravity operated and MUST be level in order to run properly.
The second thing you need to understand is that the refrigerator will not cool properly if it is too hot outside (typically over 90 degrees F ambient). The refrigerator needs good air flow across the "condenser fins" that are located at the top of the cooling unit. If you remove your refrigerator's access panel on the outside of the RV you should be able to look up and see these fins. Make sure that there are no obstructions. If your refrigerator doesn't have good air flow it will not cool properly. Many models do not come with external fans behind the cooling unit. For the RVers that love the heat, we recommend installing some fans in the back to help with the air flow.
The next thing to check is your Thermistor (thermostat/ resistor) located inside the refrigerator. It has a 4-prong connector located at your light fixture at one end and the other end connects inside the refrigerator on one of the back fins. To test this Thermistor you don't need any tools whatsoever. Provided your refrigerator is not showing any fault codes, you can turn the temperature setting as cold as it gets and disconnect this Thermistor. If it cools properly, you have a bad Thermistor.