I’m having trouble using my PA4X in Studio One 5. For some reason the MIDI monitor shows data but the DAW doesn’t. Help!

Have you checked in the manual and Midi implementation chart to see what the PA4x can do and how to set it up.
Do the same with your DAW so that you know how to set this up to work with the PA4x. (Except for basics it is very seldom plug & play)
Also remember that Midi is not audio, so unless you are using the computers speakers you will need to plug the computer audio out into the PA4x to hear anything.
If it is still not working after the above explain what you have done, how your system works and what you want to do, as otherwise it will be difficult for anyone to help.
If you are not that familiar with Midi (Your post doesn’t say what experience you have) then have a read of this https://www.tweakheadz.com/how_to_get_started_with_midi.html which will help you to understand the Midi implementation chart and get going.

Bill