Playback doesn't work with virtual drumline installed

I have just bought and installed virtual drumline, and successfully followed the steps to make virtual drumline work with musescore.

Now when I try to use the playback feature, the entire score is instantly played from start to finish, with no sound being produced. I can tell that musescore thinks the score is being played because the rectangular cursor that follows the music as it is played back instantly appears and disappears at the start and end of the score. Toggling "loop playback" causes the cursor to appear and disappear in a strobe fashion indefinitely.