Unable to connect HR24-200 to Network/Internet

My DSL provider is AT&T and I have the 2Wire 2701HG gateway.  I've connected the DirecTV receiver (HR24-200) to the router via ethernet but it's unable to get connected.  I do not have Whole House DVR - I'm simply wanting to enable the OnDemand functionality.

I'm sure there are no issues with the network, as my two PCs, BluRay player, and XBox 360 have all been successfully using the network for months/years.

I assume I need to adjust some settings for the router (e.g. firewall settings?) but I've not yet been able to find any clear info on this forum re: the steps to take.

If anyone out there has successfully enabled this with a similar setup, I'd appreciate any assistance!

Thanks!