Remove plug for 2 minutes. Reinstall.

Let your refrigerator run for at least 36 hours to give the system a chance to stabilize. Not 24, be patient.

Look at readings. If fridge is warm, replace ALL thermistors. Don't bother testing them. New ones are 10 bucks each. That's cheap, just replace them! Wait another 36 hours and see readings.

If fridge is still warm, replace Evaporator Coil Thermistor AND the Defrost Thermostat. If you are going to go through the trouble of taking everything out, removing shelves and panels and whatnot, you might as well just put in a new DT which is cheap at around 15 bucks. Make sure you seal all connections with silicone! Any moisture getting in will make these fail. Put everything back together, plug it in and wait another 36 hours.

Should be working now. If not, you've got more expensive problems going on and if I were you I would consider just buying a new refrigerator. You already put in about 50 bucks with my suggestions. And if you keep trying to figure this out, you could easily end up spending several hundred dollars more to fix an old refrigerator. Money that could have used toward a new one.