This error usually occurs when the Epic Games Launcher couldn't download the game files for installation, It is suggested to try again later. If the issue has not been resolved, please contact us including the Launcher logs.
For more information on getting the Launcher logs visit this article: Where can I find the Epic Games Launcher logs
Once you have your launcher logs generated attach them to a support ticket and we would look further into it.
Let us know how we can help you.