I'm using: XCode 9.4 Unity 2018.1 Vuforia 7.1.31
This problem is strange. I manage to build and run this project using the same XCode for iPhone 6 running iOS 11.4. With the same configuration, it only shows me blank screen on iPhone X iOS 11.4.
Anybody have the same experience with me?
You need to update to the latest Vuforia in order to fix this, the reason you only see this in iPhone X is because it supports ARKit and Vuforia has some compatibility issues since ARKit 1.5 came out.
Vuforia 7.1.34 and above fixed this issue https://library.vuforia.com/articles/Release_Notes/Vuforia-SDK-Release-Notes