Skills aren't working

I was playing Sion yesterday and it was going okay until about halfway through the game. Why? Well, my skills weren't activating. I first noticed it when I tried to use my ult and nothing happened and I ended up dying. Upon respawning we got into another teamfight and I tried to q but nothing happened again. So I started jamming my QWER buttons and nothing happened. Except the W once. But, yeah. I tried assigning the skills to other buttons but encountered the same problem. Hasn't happened since, but I thought you might want to know.