If your refrigerator stopped working and is no longer cooling, it could be related to a few different things:
# Gaskets, Temperature Settings, etc.
## Check the gasket along the door to make sure there are no tears or areas where it is missing. If you notice anything damaged or missing, replace the door gasket.
## Check the temperature settings and ensure that your temp is set somewhere between 35º and 38º (or thereabouts
# Dirty Condenser Coils
## In the back are a set of coils that your refrigerator uses to remove heat from the air inside the fridge. When these become dirty they perform less efficiently and, in some cases, may fail to cool entirely. If these coils are covered in dust or dirt, they won’t be able to do their job properly and your fridge will stop cooling. To clean the condenser coils, simply unplug your fridge and use a brush or vacuum attachment to remove any dirt or debris.
# Condensor Fan
## The condenser fan keeps air flowing around the condenser coils and prevents them from freezing up/over. You can check that this is not obstructed by unplugging the fridge and spinning the fan with your hand. If it spins freely, try removing it and checking the connections using a multimeter
# Internal Components
## There are other components that can go bad from the Compressor and start relay/capacitor to the temperature sensor or thermostat and even the control board. The only way to tell for sure is to test each connection with your multimeter.