Yes, that narrows it down.
Your problem is that you don’t have a two channel soundcard in that chain. What you are currently trying to do is physically impossible. Your computer is the soundcard, which means it is sending out the final signal to the mixer. You will have no access to any cue or preview functions as anything you plug into your computer is post-mix. You can’t listen to something you haven’t physically connected (in your case, a second channel on the mixer).
The cheapest way to fix this is to get a stereo to mono split cable. When Virtual is set up this way it will send a mono version of deck 1 through one side of the stereo channel, and a mono version of deck 2 down the other. You then plug these into two channels on your mixer and you’ll get something more inline with what you are expecting.
There are a couple of other ways you can set up a mono split cord too depending on how exactly you want to run your system.
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