I am very frustrated with this problem and the Unity3D community isn't very helpful because no one there is answering my question. I have done a ton of searching to find what the problem could be, but I didn't succeed. I installed Vuforia 1.5.10 and Unity3D 1.5.0.f. I use the Unity extension. I imported the demo app called vuforia-imagetargets-android-1-5-10.unitypackage, put the wood chips image target on the scene, the AR camera, and added a box object on top of the image target. Then I built it and sent to my Samsung Galaxy tablet. However, when I open the app on the tablet and point the tablet to the image target, nothing shows up - the 3D box isn't there. As if I didn't add any objects to the scene. I just see what the device camera sees.
Has anybody experienced this before? Do you have any ideas what could be wrong? No one online seems to be complaining about it.