10 possible reasons behind "refrigerator not cooling" - Ideas by Mr Right
I would first make sure the condenser cooling coils are NOT dirty and plugged up with dust particles? Also, frost build may also be problem may have to manually defrost it?
If you haven’t cleaned out the cooling system it may be the problem?
Some more general information may be useful?
Refrigerator Repair (Not Cooling, Defrost System) - YouTube