Midi has 16 channels and just like your TV, the channels have to match. I think the Thru channel in Biab is either 4 or 5. Under Options>properties>midi it shows all the different midi channels Biab uses. If it's 5 for example, set your keyboard for 5 then when you pick an instrument using the dropdown under the little Thru window you should hear it. As soon as you hear it, you will probably hear something else too and that's latency as in it takes up to a half second from the time you hit the key to the time you hear it. This is only when you're trying to play something live. It doesn't matter on playback. That's another whole question concerning your midi driver. Try getting some sound first and then we'll tackle the latency.

Bob

Biab/RB latest build, Win 11 Pro, Ryzen 5 5600 G, 512 Gig SSD, 16 Gigs Ram, Steinberg UR22 MkII, Roland Sonic Cell, Kurzweil PC3, Hammond SK1, Korg PA3XPro, Garritan JABB, Hypercanvas, Sampletank 3, more.