Make sure that you are operating the fridge level. The more level the better it will operate. Have you been running it out of level?
Next, have you adjusted the thermistor? It is a little temperature sensor that rides in a plastic thingy that slides up and down on a metal fin inside and in the back of the fridge. Moving it up should make the fridge operate longer, thus making it colder.
Finally, don't fill the fridge too full or it won't be able to cool effectively.
Look up YouTube videos about RV absorption refrigerator problems if things still don't work properly.
2005 22' BT Cruiser 5211, Chevrolet 3500 chassis w/6.0L Vortec V-8; 6'x12' Cargo Trailer; Honda CB500X motorcycle for street and ADV riding; Yamaha TW200 motorcycle for dual-sport and trail riding...All of it for fun and adventure!