MainStage: Audio input from interface will not pas through MainStage External Instrument Channel

Hi all,

I have tried 2 interfaces and followed the YouTube tutorial exactly. I am going a little crazy trying to figure this out.

My synth is triggered via MIDI, and I can hear the signal in my interface but it will not pass through to MainStage.

I have tried to pass audio through every channel on an Audio Channel as well, the correct channels are selected but nothing passes through. I can hear through my interface but not MainStage.

I am using Presonus Quantum and Tascam Model 12. Neither work.

Any suggestions??