Thank you, Mth! That was what the trouble was!
Yes, I did specify the alternate installation path during installation, and the server.cfg file did have the ServerRoot key pointed to c:\apps\nomachine .
However, I had a friend years ago that recommended to always install apps to their preferred paths to avoid trouble. So I uninstalled NoMachine, then reinstalled it, allowing it to install to it’s preferred path.
Bingo! That fixed the trouble.
The NoMachine team may want to still check the installation procedures — a clean NoMachine install (to a non-standard path) on a clean Win10 (winver 1909) machine should reproduce the problem for them to study if desired.
Meanwhile, I’m able to go happily forward. Thank you again! You rock!