I have setup and used IVP previously with no troubles.
Now I set it up and can hear sounds correctly routed during note entry – and when clicking individual notes in the score – but the IVP channel [Downstem Voice 1 in this case] doesn’t sound during playback. (It’s routed to NotePerformer.)
The asterisk in NP is to indicate that it is a change from the original setup. If on hits Reset, it goes away. Can’t help with the OP’s question, but this I can answer!
Figured out the problem. I created an Expression Map for the whistling section. Still don’t know why, but something about it prevented real-time playback.
Returned to the NotePerformer Expression Map for those channels, and it worked. Odd.