If the propane does not light at all, you have a supply problem in the back of the fridge.
If your fridge lights up automatically, it will bypass the thermocouple temporarily to allow the flame to get started. Once the thermocouple is hot, it keeps the system going. If there is a problem with the thermocouple, it will not allow the propane solenoid to open, allowing the flow of propane.
A manual light fridge will have a button to push in to bypass the thermocouple until the flame heats the thermocouple up.
Do take off the jet and the burner. Make sure that the burner is clean and soak the jet in rubbing alcohol to break down the oils found in propane. Do not stick anything in the jet as it can be damaged easily.
If the flame does light, but is weak, you may have a bad regulator at the propane tanks. A manometer can check on the proper pressure.