Hi!
I own the presonus studio 1824c, an external compressor and my DAW is ableton live 11. I was recently windows user and I routed everything first from the universal contol, mixers etc. and ableton was able to use properly the external audio effect. Now on my mac I routed exatly the same on my UC and the I/O in ableton and the external audio effect only receives output signal but no input signal.