[GAMEPLAY] Sion's Q stopped working until I restarted client

I haven't played Sion that often since his rework. This is probably my second time. I just finished a game with him but halfway into the game his Q just stopped working. I tried pressing 1 (I previously remapped QWER to 1234), and I tried clicking the ability with the mouse, but I couldn't get it to work. The rest of his abilities worked fine. I opened Task Manager and closed the client. Upon restarting the game, everything was back to normal.

Edit: In case you need more information, I'm running Windows 7 Home Premium, 64 bit, in NA. New computer so everything's fresh.