Vuforia 3DModel function is not working well while using.

Hello

We got an problem when developing Hololens Vuforia App.

Our application  displays a cube on top of the 3D object target.

Below is the case we meet:

1.wearing the HoloLens, the cube appears far away from the target. 

Just like the preview shows.

2.change the position, the cube still appears at the same place.

Is there any method to solve this problem such that the cube can appear just right on the top of the target?

P.S. We use free vuforia license to develop the app. 

THANKS！