I edited my post, said condenser instead of compressor i realised.
Engine off pressure dont tell you much, outside of letting you know theres no major leak.
Forst you want to see if the compressor will click on without it running. Just key it on, and turn ac on and off (fan must be on) and have someone stand next to it and hear for the clutch engaging and disengaging. If nothing, you have a switch, wiring, or compressor issue.
If you hear the click, but compressor does not come on when running right away, then yes probably a pressure sensor-low or high. If it comes on until you get warm and then cuts out, dirty condenser.
Im not familiar with that tractor, but some newer deeres also have a evaporator frost sensor that will shut it down when bad.