How to play mp4 video in HMT-1?

Hello,

I use the HMT-1 a 2D glasses and want to play a Video by voice commands. 

My current problem is that the voice commands in the ThingWorx Studio View app do not work. So far I have used the recommended voice commands like Play Video or Pause Video. I also used the German commands like "Bildlauf ein" or "Video wiedergeben". However, none of these commands worked.

Now my question. Do you have any idea what the mistake might be or could you please give me some advice.

Thanks
Laurenz