Nautilus passive not working correctly or at all.

Last game (ending at ~8:30 PST) I played Nautilus top on live servers and I noticed that my passive was either stunning for a short duration or not at all. further into the game when the passive said a 1.5 second stun, I realized it wasn't working at all. I was against lee sin, had full tank runes (armor quints and yellows, magic resist blues, and health reds) and 0/27/3 masteries, if that helps. Please fix this, I will play another Nautilus game to see if he problem persists.