Fortnite having problems with iPhone phones after updating to version 9.40, Epic Games is only able to slightly damage users. The cause of this problem has not been explained, but Epic Games has confirmed that it was a problem with Fornite who refused to launch the iPhone after 9.40, but there was a solution.
Epic Games recommends Fortnite users to delete iPhone applications, install them again, and everything will return to normal. It's not clear why Epic Games didn't launch an intermediary update to solve the problem, but reinstalling the game is the only solution to use it now.
Reinstalling Fortnite on the iPhone will not affect the progress you make in the game, and that is because everything is stored automatically on the Epic Games server. The process may take some time depending on the internet connection you have, so be prepared to wait a little.
After further investigation, iOS players can delete the application and reinstall it to resolve the update error.
– Fortnite (@FortniteGame) July 18, 2019