One of the first things you may want to try is to adjust the internal temperature settings. Often, a fridge will have a dial with the numbers 1-6 on it, 1 being warmest, 6 the coolest. Fiddle with this till it's just right.
Make sure that it is probly hooked up to the water and electricity and that the outlet it is plugged into is designed for high voltage of fridge and is plugged up. I would also check on the coil in the back and make sure that it is not dirty or overheated
Your trouble shooting process shout start from simpler to more complex steps. First of all concentrate on dirty coils of condenser; then check whether temperature regulator is working properly. If problem remain unsolved; then ask a technical person to view the compressor of your refrigerator.
If the refrigerator is not cooling properly find the adjustment switch and raise the cooling level manually for example cold to colder to coldest. De froze the refrigerator once again allow to restart the process once again still didn't work call to an electrician or to customer service operations of the particular refrigerator for a repair.