Vuforia Video PlayBack Error Android

Good afternoon sirs! I'm developing an augmented reality application with Vuforia. I followed this tutorial in detail Text Tutorial and followed this video that follows the same documentation Video Tutorial. I'm using the package "vuforia-unity-6-0-114.unitypackage" for my application and the package "VideoPlayback-6-0-120.unitypackage" to display the videos. I have run the application on my device and the only thing I see is the error icon of the vuforia. I even rode the example of the default scene provided in the package but it gives the same error.

I'd like you to help me spot the problem.