@k2347,Reasonable request. Since you're recording as a loopback, I dont know if that will be switchable for Main or Alt monitoring. I'd susoect there is Harrison audio interface software for directing your monitoring to either of those locations. In other words, not looking in your Windows Sound driver settings, that youre hunting for. Also, what is displayed not just from your Windows Sound path, showing drivers, but instead what is shown from the Studio Pro Input selections? There, you'd see Instrument as well as loopback sources. Hopefully, an additional source for monitor Main and Alt select. Also, check your Studio Pro routing for Ouputs by clicking the I"/O" at top left of the mixer area (as I recall, I'm away from the computer).
In short, I'd bet there is routing software from either your Harrison Mix layouts, or Studio Pro input, and output settings for directing signals to those two monitor outs. I agree, you should be able to set either in tandem, or split monitoring. Basically, right on the fly, although that is becoming less available with many designs now.
The Windows Sound selections are only one stop, global settings. Not where you should be looking.
Also, the ball is in Harrison's court. Customer service should happen right away, or they're showing their hand right out of the gate. Never good.
I had what I thought was a driver issue with Audient, and I hooked up with Audient the next day. Due to they are located in England so thete was a business hour conflict was all. Spoke with their main engineer after that on the phone. Or should ai say, "tellie".
Looks like a dynamite audio interface.
Let us know what you find.
Sweetwater will try to contact Harrison support for you, but that is likely it.