I have a gss201emb it is not getting below 50 degrees I have replaced the main board and the defrost coil is fine . Need some suggestions hope someone can help.

Check the coils under the unit. You should remove rear cover (with unit unplugged) and on the right you will see the coils. See: https://dl.dropboxusercontent.com/u/8010163/GE_Profile_Artica.pdf
Spray them down with "409," "Fantastic," or another good soap and wash out with a quick spray of water from a water hose nozzle. Make sure to clean the fan, too. Look at the cover and clean any air vents, or on this model you may not even need the rear cover, but DO NOT try keeping cover off on other models because it's needed to route air through the coils, the kind that are laid out in a rectangle under the unit. Run the unit and it should work unless you damaged the compressor.