Thanks for the reply, and the questions. Here are some answers.
I can't get any of the B3 sounds to play. For the Vox group, the 96 Beers preset works as it should. I can't find another one in that group that does. All of the piano presets seem to work okay.
In the Reaper mixer, when sound is being heard, the yellow bars move up and down normally. When no sound is coming out, a narrow red bar moves up and down (right channel only, apparently).
The "onscreen keyboard" is the one that appears in Arturia. Those keys (clicked with a mouse) produce sound as expected. When I use my MIDI controller, those keys also look like they are being played, but no sound is produced.
Thanks again for any and all help.