I had this problem. I tested on simulator. I left the “Launch screen file” blank and removed the line about the “launch screen file” inside the plist. I restarted Xcode. Nothing. In my case in was not black it was white. Xcode 7 target ios 9.
i read this one as well: Launch Image does not show up in my iOS App
The launch image only showed up when i deleted the app from the simulator and run the app again.