Camera with Static Device Tracking can't show images

Hi,

I use a static camera, so i try to set it on unity with vuforia.

I fellow the develop library here: https://library.vuforia.com/device-tracking/enable-device-tracking-unity, but get a black screen.

The camera connected to the laptop did not return any data， but the game object in the scene can be rendered. 

My unity version is 2020.3.25 and vuforia version is 10.5.5.

Here is the code i use:

    private void Awake()     {         VuforiaBehaviour.Instance.DevicePoseBehaviour.SetStaticMode(true);     }

Without the code, everything is right.