If you got caught out by this simple mistake, don't worry - many many MANY people have made the same mistake (even ME perhaps? ;-)
PoEL is designed in such a way that it seem obvious to plug power in to the power socket and then plug the ethernet plug into the router. BUT, would you believe, it does NOT work that way!
The correct way to use PoEL is to use an ethernet patch cable to connect the ether SOCKET of PoEL to the router, like so:
The apparently obvious way to connect it is actually wrong! :-D