I just want to say. I've had this problem for years. Usually the first xbox to connect is the one that will connect to ea. My second boot-up always fails to connect. I've had a few random times they both worked. It's weird to because we play Battlefield 3, 4 and do really well. It's always a good game... Then suddenly you get kicked (it seems like) and you cannot get the 2nd xbox to connect ever again. Now I'd tried everything. Resetting the systems, the order, the router, the cable modem....etc. Nothing works...
Except.
One day i went out and purchased a Nighthawk router. And boom.
Never had the issue again.
It was ever plug and play setup.