Verify the compressor is running by removing the back cover you can listen for it but dont be confused by the noise coming off condensor fan motor. If the compressor is running pull the back cover off inside freezer section and look at the frost pattern on evaporator if it is heavily frosted you have a defrost problem, if it has a big ball of ice at the beginning and the rest of the coil is dry you have a leak, restriction or inefficient compressor, in that case you would need a certified tech to repair it and you are looking at a repair of 300-600 dollars..... maybe....