Sejuani W Bug

So I just finished this game. I played as Sejuani. Everything was fine until late in the game, after my teammates took Elder Dragon, I found out my W didn't work. I could still press it, it would be on cooldown, but there was no animation of W, neither was the damage of W. So basically I couldn't use my W no more. I don't know if it was triggered because of the Elder dragon or just a coincidence. Please look into it, thx!