After finishing Hexcells Plus and Hexcells Infinite about a billion times each, I figured I'd get back to this one, but I noticed that for whatever reason, the sound effects have stopped working. The music still plays fine, but there's no sound when I select a saved game, reveal or clear hexes or finish a puzzle.

Restarting the game or turning sound off and on again doesn't help, and I can't find a separate option for sound effects. Hexcells Plus still works fine. What gives?