I'm using Vuforia 6.2.10 to render some models on markers. It worked until I upgraded to Unity 5.6.0f3 this weekend. On Android I get a black screen on the AR Camera.
I don't see any errors, when i check the logs It appears that he detects the markers etc.
Sounds like possible migration issue. Running the VuforiaSamples 6.2.10 / Unity 5.6.0f3 app on a GS6 worked fine.
https://library.vuforia.com/articles/Solution/How-To-Migrate-a-Unity-Project