Keyboard / Consumer APIs don't work?

[DesktopFolder]

Trying to get media playback working with Arduino Pro Micro.

With the built-in keyboard library, everything works fine.

With this project:

• Consumer MEDIA_PLAY_PAUSE does nothing (key tester applications don't even register a keypress)
• Keyboard keys e.g. KEY_F15 just send unrelated keys like O, P, Q

Is this a missing configuration somewhere? I tried directly copy-pasting the example Consumer API .ino file and this did not work (same issue as above - no keypress registered, no indication anything worked). The Keyboard API similarly seems to not work. I've searched far and wide for any way to do this but am giving up hope...