Hello again after four years (and sorry for necroposting this thread, admin).
Since four years is a big advancement in tech, let me fill you in.
Windows 10 Pro x64, Corsair K68 RGB.
Your 0.2 plugin works just fine; without the need to run as admin and when XMPlay is running in the background. You're right, Logitech must have did something to the multimedia keys, so that they are not recognized when the program is in the background.
I haven't mentioned this four years ago either, but when I used the older plugin, even with the newer keyboard, play/pause immediately re-played the song, rather than just pausing. 0.2 fixed that. I must've not noticed.
Anyway, I came back just to let you know what would happen with a different keyboard.
Logitech is to blame. Thanks again.