I've been trying to use the Vuforia AR+VR Sample on iOS and the default scene works fine detecting the astronaut and switching between AR and VR.
I'm having some problems, though.
If I add a ground plane it is not detected on runtime. When I touch the screen to place an object on the ground the console says the device tracker is not initiated. I tried enabling it manually but it gets shut off automatically. I'm trying it on an iPhone 7 with iOS 12.