Lexicon IO42 Audio Interface Doesn't Appear

I have been using a Lexicon IO42 audio interface with my late-2015 vintage MacBook Pro. I just bought a shiny new Mac Mini (3.0 GHz Intel I7, 16GB RAM, 500GB SSD, macOS 10.13.2) to replace the MacBook, but when I connect the IO42 and look at the Sound preferences panel, I don't see it. For Output devices, I see Headphones and my HDMI monitor. For Input devices, I see none. If I move the USB cable from the Mini back to the MacBook, the IO42 shows up immediately in the Sound panel, so I know it's not a problem with the Lexicon.

I don't recall having to do any configuring on the MacBook, in order to make it see the Lexicon. What am I missing? How can I confirm that the IO42 is compatible with the Mini/High Sierra?

Thanks.