Make sure that the condenser coils are not covered with dust. You can clean the coils easily with a rag or vacuum cleaner with a brush attachment.
Unplug the refrigerator for 1 minute, then plug it back in. If your refrigerator is in demonstration mode, unplugging it, then plugging it back in resets the refrigerator to regular mode. If none of these actions resolve your cooling problem, may be refilling the gas could be the solution, please contact the manufacture.