I have grabbed World Of Goo from the Epic Store today. The button used for installing the game is unclickable and it says “Owned”. The game is nowhere to be found in my library, nor is it in my downloads. I have tried running the Epic Games Launcher as an administrator, and tried redownloading the program. Nothing seems to work.
I also tried to download it once, but everything is fine and there is no problem you described.
I suggest that you better contact the relevant person in charge.