We have had the same version of Vuforia and Unity for months now and it has always worked as expected. The last few days we have rebuilt our project (we changed the icon of the app) and all of a sudden the tracking doesn't work.
Pointing the camera at the mark results in nothing happening. The camera stream works, but the object doesn't appear on the mark.
Version of Unity - 5.6.1f1
Vuforia - 6.2.6
We haven't changed a single thing!
It works with IOS (albeit it takes longer to load now) and it works using webcam. but nothing with Andriod.