6 Channel USB Audio Interface

I’m using a TASCAM US1200 USB Interface to feed multiple mics into BoinxTV. I can’t get more than two mics to be heard while using it. I have a segment where I need three mics to be heard and I am struggling with it right now, is BoinxTV unable to record more than 2 tracks or do I need to use a different program to record the audio, like GarageBand and sync in post? Any help would be great.

BoinxTV only captures stereo inputs. If you can set the device to stereo mixdown, you will receive all inputs mixed down to two.

At the moment there is other way to do this.