If you're not having any luck with the USB recording, how I do recordings is an RCA to 3.5mm in on my computer. On the back of the mixer near where those USB ports are, there is an l+r for "rec" out. You need an RCA to 3.5mm cable, and plug it into that port on mixer, then into the line in on your laptop. You should then be able to select that interface in audacity and record through it. Mainly suggesting this way as it is the standard, + I don't have any experience with that direct USB record (also don't have that equipment with me to do any testing with)