[GAMEPLAY] Fizz E became uncastable for long duration

My E became dark, unclickable, and uncastable for about a minute within a game. It appeared castable again only when I took damage. I sat in the fountain for about 30 seconds trying to cast the "dark" E to no avail. The enemy team was rushing in to base, so I needed to fight. When I entered the fight and took damage I was able to cast it again.