Port failed to open - already in use? The old posts on this, didn't do me any good

If I understand correctly, last month you were at this point:

Were you successful in updating the firmware?

USB communications in Windows tends to be unreliable, at best. The usual steps may be helpful at weeding out the easy gotchas:

FWIW, I just replaced a USB-A to USB-C keyboard cable that worked fine for a year and is now just slightly touch-sensitive, so things can fail with no warning.

Let us know what you’ve done and what happened, so we help you make some progress.