I got error on a simple AR code

I’m new to Unity and I’m making an AR project now with vuforia package.
I followed the steps exactly the same and it shows the error when I run.
I use integrated camera on my laptop and it blinked once after I run, but then it shows the following error :

Exception in callback: Failed to create ImageTargetObserver: DATABASE_LOAD_ERROR.
UnityEngine.Debug:LogErrorFormat (string,object[ ])
Vuforia.Internal.Utility.UnityLogger:LogError (string,object[ ])
Vuforia.Internal.Utility.Log:Error (string,object[ ])
Vuforia.Utility.ExtensionMethods.DelegateHelper:InvokeDelegate (System.Delegate,object[ ])
Vuforia.Utility.ExtensionMethods.DelegateHelper:InvokeWithExceptionHandling<Vuforia.VuforiaInitError> (System.Action`1<Vuforia.VuforiaInitError>,Vuforia.VuforiaInitError)
Vuforia.Internal.Core.Engine:InitOnCameraReady ()
Vuforia.WebCam:HandleFirstWebCamFrame ()
Vuforia.WebCam:b__33_0 (bool)
Vuforia.Internal.Utility.VuforiaCoroutineUtility/d__1:MoveNext ()
UnityEngine.SetupCoroutine:InvokeMoveNext (System.Collections.IEnumerator,intptr)

Are there problems with my DATABASE?
Thanks in advance !

You might get better traction for this question in the Vuforia forums: Getting Started | Vuforia Library