Lux E cannot be executed!

I just played a ranked game and everything was fine up to minute 15. I casted my E onwards Heimerdinger but the spell didn't even appear and the spell has never been executed although the character itself motioned to cast the spell.

From that point on Lux E was available anymore. Despite relogging and restarting the client twice the spell wouldn't be available for the rest of the game (!).

Of course we lost that game because a carry's damage was almost fully taken away...

Please fix it! If necessary, video material is given and can be shown as evidence.

Greetings