Unit will not stay cool. Is it a thermostat, compressor?

Small refrigeration units like this one like to fail to cool by developing a small leak and slowly
leaking refrigerant.
THERMOSTAT FAILURE CHECK:
A technician will check the thermostat using using a DMM (digital multimeter). But you can suspect the thermostat if you set the thermostat high and the compressor motor does not run,
then set thermostat low, and the compressor motor also doesn't run - in other words, the thermostat is failing to start the refrigerator's refrigeration system no matter what its setting - an obvious failure of the thermostat.
COMPRESSOR FAILURE CHECK:
If the compressor is dying, you would hear the compressor running almost constantly, but not
sounding quite right (uneven noise, clunking, tapping).
REFRIGERANT LEAK CHECK:
If you unit is low on refrigerant (due to a leak), the compressor motor will be running
almost constantly, but it will sound Ok.

My Darby Designer wine cooler temperature will not go down. The upper chamber stays at 71 and lower at 68.

Wine cooler how to check thermostat and where is it.model dwc283bls compressor doesnt run and cant set temp