So one thing I might want to point out to the other person who also said they were having this problem, and what seemed to be the quirk for me. Try plugging in your Kindle AFTER you've started up Calibre, at least for the first time. This is what "kickstarted" it for me and got it to recognize. Time will tell if I have to do it in this order every time, but indeed the first time it was properly detected was when I did it in this order so you might want to give it a try yourself if you're still having trouble with the K2 detection.
