Back to the facts. You've seen it work linked. But what did you see? In 2 player set up, or with 4 players?
It makes no sense for 1 ethernet port to have the leds lit up, if the other machine's ethernet port is bad and has no leds..
If you have a switch or router, connect both machines there, do both machines have a lit up ethernet port on the back then?
And on the router's port indicator lights?
(Set them as 3 machines or something, perhaps this has to do how the ethernet port behaves?)
This can just be a router w/ no internet, just a power supply. We need to know if those leds light up.
Did you try and set them as 3 machines using the cross cable, does that work? (albeit with a complaint it can't find machine #3)..