@PDalton81 

Hi, welcome to the community.

In order to create the Powerline Backhaul via Deco P9, you have to set Deco P9 into the main Deco.

General Questions about the Powerline or PLC Backhaul Feature of Deco

So considering you are still using DSL internet service, Deco X73-DSL has to be connected to the ISP Openreach box or DSL box directly. Is there any specific reason that you wish to replace the original Sky router with a Deco X73-DSL? If not, we could still keep the original Sky router, then turn off its WiFi and connect Deco P9 to the ISP modem to provide a Mesh network over Powerline Backhaul.

Or if you wish to keep Deco X73-DSL, you could start creating another Mesh network via Deco P9 on the Deco APP>"+">"create a network"

Thank you very much and best regards.