When I first posted this, I had not rebooted after updating the Host software. I then rebooted it, and still had the problem. However, when I just tried it, it is now working. Not sure how to explain that. Perhaps I got confused, and did not actually try previously - after the reboot. Perhaps something is intermittent.
If it happens again, I will pursue further.
In answer to your other questions:
I was trying to enter the password on the Windows login (lock) screen. It recognized CTRL-ALT-DEL, the Cancel button, and the password enter arrow button. It did not recognize keyboard input, or clicking on the ease-of-access icon.
This server is running Webroot Secure Anywhere. If the problem should recur, I'll try disabling that, and see if it makes a difference.
Thanks for all your diligent assistance.
Edited:EJ - Sep 06, 2017 10:02:05 am EDT