Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
Since I didn't hear back before the 4th of July holiday, when I'd have extra time, I just wiped everything from the drive and reinstalled my Windows 10 operating system. Then I immediately uninstalled all the Office products, and attempted to download and install my volume licensing version of Office 2016. It worked!
So whatever problem had prevented the earlier installation was eliminated by wiping and reinstalling the operating system. And then I re-loaded all my other software and data files after Office 2016 successfully installed.