Reproduce bug:
1. Open an AR sample, i.e. Image Marker sample, until AR camera has been already loaded.
2. Press device home button
3. Quickly open AR application again, the screen becomes black.
This problem only occurs on iOS not in Android.
I have tested on iPhone 4S, 5, 6, 6+, iPad 4 with Unity 4.5.4 and Vuforia 3.0.9
Anyone has the same problem? Please help.
Thank you in advance!
see latest posts in the thread you refer to:
https://developer.vuforia.com/forum/vuforia-40-beta/camera-not-opened-and-screen-black-vuforia-40-beta