Refridgerator runs but doesn,t cool - GE GDS18LBR Bottom Freezer Refrigerator

Check that the compressor is running , if it's not it could be several things causing this,
defrost timer stuck in defrost, thermostat not making on a rise in temp or compressor is stuffed or last but not least no gas and or one or all of the above.
Check that the compressor runs ,spin the fridge around and you will find a cover, remove the cover and you will find a black round object the size of a grape fruit, with it plugged in and in the on position place your hand on it , be careful not to touch any wiring .
if it's running you will feel it ,if it's not it will be cold and then you need to check all he above , to check these devices you will need a multi meter and make sure you unplug the fridge.