I'm going to assume you are using a TiVo & not a V6... check here if you're not sure.
The Ethernet connection is only used for connecting multiple TiVo & V6 in your home, if you only have one box, then it's not used.
As far as using OnDemand & Streaming apps are concerned, the TiVo has 2 issues...
1: It's fundamentally an old box, and doesn't cope well with the streaming apps. There's no way of getting around this, changing to a V6 if you can - is absolutely the way to go.
2: The onboard internet fails, rendering the box offline with no internet connection. On the front-left of your box there's a series of green lights. Second from left has a "heart" symbol painted and is the online light. If this flashes, the internet is offline so anything that uses the internet, won't work. That's a fault.
You're best calling Virgin Media in either instance - either to discuss a box-swap/new package deal, or to report your faulty box.
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