@TP-Link Well, what's the answer? You didn't leave a solution.

@petey 

The Deco WiFi Mesh System requires one of the Deco units to remain connected to the source of internet.  It appears based on what you said here that this is not the case, hence the red light.  What you would need to do is connect one of the Deco units to the router or source of internet.  This will then provide internet service to the other Deco units in the Mesh network.  From there the unit that you connect to the TV should have no problem providing the TV internet.   If you bought a single pack and only have one Deco you would need to purchase at least one more unit to accomplish what you are looking at doing.  

Also please note that the Deco itself is a router so you can replace your current router with the Deco, just be sure you still have a modem compatible with your service as the Deco does not replace the modem.

@Carl Thanks Carl...that's exactly what I did.

So lemme get this straight...ONE of them must be CABLED into the router or just connected wirelessly?

THEN I can connect the other one to the TV with an ethernet cable? Am I understanding this correctly?

Thanks so very much for your response. I was gonna pack it up and send it back and hook up a powerline adaptor.

Lemme know please.

@petey 

One unit must remain connected to the internet source at all times.  It does not matter if that source is a router or modem.  After that unit is setup and connected the remaining units can link to it.  For all units that are remote the 2 ethernet ports can be used by Clients as LAN or as a link to other Decos for Ethernet Backhaul.  Ethernet backhaul is faster than having the Deco units talk to each other via wireless but is not needed for the system to work.  All that is needed is that all units must be configured and one unit must be connected to the Soruce. 

@Carl Thanks so very much for the clarification Carl!! I'll give it a shot and yes, I connected the one Deco to the router wirelessly and connected via ethernet cable to the TV expecting it to work. Now I understand.

Thanks again. I am most grateful.

Pete