Changing the extension of the "video" file to .webm in the "WebM source" property, I managed to go through the menu, the selection and have the audio of the file play in Firefox. (I've tried checking the video file on VLC anyway, it seems to just be audio, I never saw any image).
In chrome, whether named .ovg or .webm the file never played.
Perhaps a bug with chrome, perhaps an issue with the video file you are using (which doesn't seem to contain video anyway).
Also, the console in Chrome does not send out any message.
When using the extension .ovg, Firefox returns a 404 file missing error.
If it is supposed to be just audio, don't bother playing it as a video, just use it as audio (like you've done in the rest of your project).
Also strictly bumping a topic for several days when adding nothing new to it is not the best idea.