Black screen on iphone

Hi all, I use Unity 2018.3.14f1 but i tried other versions. I use Xcode 10.2.1 . My game plays perfectly on unity and i build it on unity without error. Then i build on Xcode without error and run it on my iphone 6 (ios12.2 ) but it shows just a black screen. My Camera>Clear Flags is Skybox and its color is blue on Unity. How can i fix this. Thanks.