Drivers for the interface are installed, I can use another application to open up the port and see some of my debug messages from the device. It is an Adafruit FTDI friend connected to an Arduino Pro.
When any FTDI or CH340 device is connected to this Windows 10 system, the “Tools → Ports” option is greyed out and not selectable. Curiously, the 8u2 and 16u2 USB to Serial interfaces work fine ONLY when no FTDI or CH340 based devices are attached to the system.
As a band-aid, I am able to upload to the port by changing the value in the “preferences.txt” file.
I need a serious solution for this nuisance.