This happens to me a lot when I browse from my phone. I think it's a mobile setting, as the volume on the TY video itself is muted and I have to turn it up to hear it. Personally I like this as it often inadvertently tap things on my small phone screen and it will start playing loudly.
If the volume on video itself is on as well as the master volume on the tablet, them I'm not sure whats going on.