I'm not sure if it really helps much with me adding another voice, but I'm having similar issues here.
Macbook Pro -> Wizard -> MIDI keyboard ..
I'm able to load patches on to the Wizard (slick way of loading patches via the browser BTW - I like it!). I'm able to trigger notes on the Wizard using the virtual keyboard in Chrome .. the knobs and buttons appear to work fine.
However, at the moment pressing keys on my [Roland] MIDI keyboard (connected via the USB host port) doesn't appear to be triggering anything on the Wizard. No flashing light. No audio. Nada.
It's definitely not resetting the device, or anything sinister like that (If I leave a note playing that's been triggered by Chrome it keeps playing while I'm banging on the keyboard)..
I've verified all of the connections. Everything seems good. The MIDI keyboard is working fine as I can capture events using MIDI monitor when I plug it into my Mac.
I thought I'd found the issue when I checked the USB settings on the keyboard and they were set to use a "VENDOR" specific USB protocol rather than "GENERIC". Unfortunately, I fixed that, and still no luck.
So, to confirm, I can trigger notes on the Wizard using the USB interface that's exposed to the Mac, through Chrome, but it doesn't appear to be listening on the other USB i/f.
If there's anything that I can do to help debug, I'm more than happy to help.