In order to get *any* device to shake hands and play well with a Cox Panoramic gateway it's essential to know the inherent limitations of relying solely on WiFi with hopes of extending an existing network. In my case, with the Airport Extreme, the signal to it is supplied via cat5e ethernet cable, and *not* WiFi. I have not bypassed the Cox device, merely adding the Extreme to the network via direct wiring. Much as what you have experienced, there will inevitably be a severe reduction of that WiFi signal. Distance, in this instance, is the culprit.
Depending on the integrity of your existing coax, you may be able to provide extended WiFi coverage with acceptable signal strength using a MoCA adapter/device, such as what I presume Cox offers at $179 installation fee plus monthly charges. It's a branded Actiontec 802.11ac Wireless Network Extender with Gigabit Ethernet & Bonded MoCA (WCB6200Q02), available on Amazon, ebay and B&H Photo, allowing you to extend the range of your WiFi network utilizing the coax wiring already in your home.
