Try to make this short as possible:
Fridge with freezer on top, unplugged it to defrost for house move.
Plugged it back in at new house, all was good.
Left doors open while wiping down the inside. Next day, fridge and freezer were both warm, but fan blowing in the freezer.

I ran ohm test on compressor and it looks good.
Tried a new run capacitor, still same results. Warm air in freezer, nothing in fridge, compressor not hot, coils not cold.

So it this the start relay or a defrost thermostat or something completely different?

Thanks for the help!

Was the unit tipped on it's side or back during the move?

If yes you should have left it unplugged at the new location for 24 hours.

Here are your parts, includes a wiring diagram.
Parts for Frigidaire FRT21NGJW2 Refrigerator - AppliancePartsPros.com

You could check across the compressor/PTC to see if it has 120 volt.
This would confirm that the wiring is OK, if you have 120 volts there.

If the compressor is getting 120 and it should as the evaporator fan is running and it is wired in parallel with the compressor then I would try a new PTC.
There is no reliable way to check the PTC so you just have to try a new one.

Note that a compressor's windings can check out OK and it may still have a problem. I am assuming that you checked the winding resistances and also that they were not grounded.