You have to get the HDPro on the local Ethernet network before you can advance. That is the initial main goal. I assume the power LED is turning on. You purchased a reburbished unit, from who (woot ??). Make sure the power supply is rated for the HDPro SB. My power supply has specific indicators for which slingbox device it will work with and which devices it will not work with. My pwr supply has these output ratings: 5DC volts, 4.0 amps
Does your HDPro see the Ethernet signal downastairs, i.e. Is the network LED turned on RED when the HDP boots up? Do other Ethernet devices work on the same adapter you are using with the HDPro, at the same location downstairs? If other devices work, it may be the Ethernet port on the HDP.
If it does not see the Ethernet signal, try moving the HDP directly connected to the router. See if it shows up on the local network. If it does, you can configure it for the ports you will use with your cable box, etc. The setup program will indicate "no signal found" as you run through the configuration, but it will configure the HDP for whatever settings you make. Then move the HDP back downstairs and connect it to your TV/cable system.
If the router still doesn't see the HDP, on the Ethernet, I'd say therre's a problem with the house network/power line adapter.