[game play] lux - activate to detonate my E

During this ranked game, I wasn't able to detonate my E as Lux after some in-game time. It says "you can't cast it right now" or similar language. It happened after casting E first, but wasn't able to detonate after. It just grayed out as if my E was still active.

I tried reconnecting, closed client and reconnect. No luck. Not sure if this was one time thing.

Here's what I think. Since I went perfect this game, I'm not sure if death would help me reset the thing but almost the whole game I'm without E to cast.