Gragas q not working

So I was playing a ranked game as Gragas and about 7 minutes into the game my q just would not go off. I left the game and reconnected and the problem was still there. Then when I put my mouse over the spell it said that Gragas' q required 0 mana and 0 CD reduction. It happened after I used his q spell once and then the barrel disappeared without exploding and i couldn't use my spell ever since.