Are you enabling the HereSphere web API when using XBVR? You need to press the icon that looks like a play button overlaid on 4 tiles to the left of the url input box. That'll load the web API, which will allow you to stream the videos in VR. If you only use the XBVR UI in the web browser, then the videos probably won't play properly, because it's relying on the embedded web browser to play the video.