After pressing Start AR, the screen is black. It still renders planes occasionally and when you put a surface really close to the screen, it renders slighting in the black.
This also occurs in //UE4/Main at CL 9440266
Result: The screen is black besides the Show Debug Menu
Expected Result: The camera renders the environment correctly
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-81660 in the post.