This thread helps Fix FortniteClient-Win64-Shipping exe - Application Error while the Epicgames' loading screen was complete.
Possible solution: before launching, try exiting the launcher from your system tray and relaunching.
Please reach out to Fortnite Team@ goo.gl/gVWM56 if that error msg continues to happen to you.
Other voices on the web: 1. move the error box to the corner of your screen(Or in a preferred area) and you'd be still able to launch the game and play later. 2. Perform a clean boot on your Windows. And, check if you're using some antivirus software. If yes, uninstall all of your antivirus and see if your game works again. If it does end up fixing the problem, when you add (re-install) your antivirus back, and you will need to find a way to add an exception to that program directory and any executables that Fortnite and Epic games utilize, including the BattlEye service.
3. Try to find the ForniteClient-Win64-Shipping.exe in the game folder (ie, EpicGames/Fortnite/FortniteGame/Binaries/Win64 (basically where you installed the game). Right click it, go to properties and just run it in compatibility mode for Windows 10 or Windows 7.
4. changed power saving to high performence. 5. run the ForniteClient-Win64-Shipping.exe as administrator. 6. Try reinstalling DirectX, such as DirectX11.