Fortnite is not installed ERROR?

When starting Fortnite, I get a message in the Epic Games Launcher that Fortnite is not installed, but I never uninstalled the game and still see the shortcut on the desktop. Fortnite is also greyed out in the launcher and I can't uninstall it either. I do not know what I should do, I also contacted the support but also wanted to ask here.

I've had that before… Just reinstalled your Fortnite.