Playback does not work with MIDI controller enabled

I'm getting a really weird problem, when I have a MIDI controller connected for note entry, playback does not work. Not just that there's no sound, hitting the play button causes all editing buttons to grey out as normal but absolutely nothing happens on the score. No sound, no scrolling playback marker (indicating that just the sound/volume is the issue).

Restarting MuseScore does nothing to fix the problem. I don't want to deactivate my MIDI controller just to listen back to what I'm writing. Anyone else had this issue?