Audio mixing in Webpresentor via front USB?

I purchased a Webpresentor to capture video footage (sony HDR CX450- consumer - hdmi out) ; mix it with audio line out from an audio mixer and send via USB for recording in OBS or other. The camcorder micro out in HDMI is unwanted and should be muted. The manual indicates how. But when connecting the front USB (of the WP) to my PC I only see the confirmation that "SW is up to date". (I have no Teranex panel) -- what am I doing wrong? Thanks for advise..

The front panel USB is for updating software only I believe, you would need to use the inputs on the back of the unit to feed the audio signal to your stream/recording. Use either stereo in or Line in.

There is a USB connection on the back of the unit that will send a "webcam" signal to your streaming laptop. But I don't think you can connect anything to the WP as an input via USB I'm afraid.