I suspect it’s something about how the LaunchKey Mini sends MIDI data — a few other people have had issues with specific MIDI devices.
This thread has a list of known-working devices: Working MIDI devices - #12 by joeman
This one has a workaround that you might try: [SOLVED] Midi keyboard isn't working with mm
(Edit: see also this post: Sending midi from Akai grooveboxes - #4 by offthesky)