You said that you have a controller button able to run the compressor.
Was that done by moving the compressor to a different Relay output on the Digital sidecar? I only ask because you could break the compressor code if you try to access the same Relay it is using.
I'd suggest testing your wiring setup by running the example compressor code provided under the pneumatics folder for
Solenoid With Compressor.lvproj in:
Getting Started -> Support -> Find FRC Examples...
That'll isolate the problem to being code vs hardware.
Open up the front panel of that example to see a demonstration of the proper wiring.
It can be executed using the Run button in the upper left of the window.
You do have to set the IP to match your team. Do that by right-clicking on RT CompactRIO Target (10.0.0.2), choosing Properties and setting the IP to 10.41.10.2