ADSL CPE P-663 Series | X-Box 360 connectivity

I have a P-663HN-51that was supplied with my Frontier installation. I can't get either of our X-Box 360's to connect to X-Box Live. Sometimes they will connect to the internet, but never to X-Box Live. It always connects to the LAN. What can I do to resolve this problem? The computers and 3DS's connect without any problems.

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