Volibear Passive not activating. [GAMEPLAY]

About 10 minutes into the game playing as Volibear my passive just stopped working. It had gone off a couple times before, but this time it came off cooldown and it just never activated, I could get down to 100/4000 health and it wouldn't trigger. The icon showed it was off cooldown but it just never triggered.

I've played about 100 games as Volibear in the past couple weeks and this is the first time it happened, didn't do anything different except for buying ninja tabis around the time it stopped working and I'm pretty sure I've done that before. I haven't had a chance to try and recreate the bug, but like i said 1/100 games so it can't be something common but definitely lead to a lot more deaths that I should've had which is frustrating, especially in the late game when it's denying you around 1200 health.