Yes. Thanks. ("wall warts" - indeed).

I believe that I have determined the problem is the USB port on the Scarlett.
I booted up my old Windows 7 machine where I used the Scarlet originally.
(It took a VERY long time for the machine to "settle" since it hadn't been on for several months).
Got the same results - the USB light did not come on.

I then connected an Alesis Q49 via the USB cable that the Scarlett uses.
The Q49 connected (and loaded its drivers). So that worked. Not a cable problem.

Interestingly, when I unplugged the Q49, I plugged the Scarlett back in - and the light lit!!
I transferred it back to the Windows 10 computer.
It lit up. For a minute or so. Then went off. Then came back on. Back off.
I can SOMETIMES get it back on by jiggling the cable (seldom works, though).

Best guess is that it is a bad USB port.