[Gameplay] Lux E disabled

When i got to level 4 i had leveled my "E" for the second time. All of a sudden, when i wanted to use it, the icon turned grey, and i couldn't activate it. Just like if i hadn't leveled it at all. I tried leveling it up yet another level, dying, reconnecting to the game, nothing made it work again, and i don't know what made it happen. I don't know how to add a screenshot to a bug report :/. Hope this gave some kind of useful information :)