ac750/ex3700 Wont connect to router with an ethernet cable

I am trying to setup a ac750/ex3700 as a new wifi hotspot. I connect it to my home eithernet cable then to my router in my basement, but the extender light for the router never comes on. I tried plugging it directly into my router with three different short cords and it still doesn't recognize my router. Since it doesn't recognize my router, I can't login to the mywifiext page to update the firmware on it. This is my second range extender, my first one I had problems with as well but it turned out it was a bad cord. This second one is for a different part of my house.