Freezer in my refrigerator not working

My freezer thawed today and is not cooling down again. The fan in the freezer is putting out cool, not cold, air and the fan in the back of the refrigerator is also working. The unit beside the fan is not turning on, not sure if this is a motor or a compressor or what. I don’t see any coils to clean and have cleaned all the dust bunnies with the vacuum underneath and in the back where the fan is. We tried unplugging and then plugging back in and nothing different. Also tried turning the temperature control in the fridge to off and then back to cold, the fan stopped and came back on when we did that.
I suppose I need to call a repair man but thought I would see if anyone had an easy troubleshooting option.
Thanks!

If the unit is not cooling, then the compressor is not running. It is always the overload and relay combination that is mounted on the compressor. It just plugs in and has a few wires. It is cheap, and easy. Don’t call the tech. You can do this. Tom http://www.applianceeducator.com