Xerath Arcanopulse Locked Out

Was playing a game as Xerath, died, and for the rest of the game was unable to cast Arcanopulse. I originally figured something got randomly remapped wrong in my game client or gaming keyboard, but everything seemed fine there. I then tried clicking the action directly and still got no spellcast, just a little "click" audio cue. The error persisted until the end of the match.