Try using Bluetooth from your phone- if it doesn't work, make sure the antennae on the AVR are snug and not laying sideways- they need to be vertical, above the top of the chassis. If you added something (like a new TV over the rack) or moved your equipment, it's possible that something is blocking the signal or the antennae were moved.
I would recommend hard-wiring the network connections to ALL media devices, as I posted. It just works better and doesn't cause congestion on the WiFi network.
If you have U-Verse and they gave you an Arris gateway, I would recommend using a better router and turning off the Arris WiFi- their hardware is crap. Set up the new router as an access point and run a cable to the AV equipment, with a switch that has more ports than the number of pieces of equipment- you WILL eventually need more in that area.
TrendNet, Luxul, NetGear, Cisco and other companies sell Gigabit routers and switches that aren't terribly expensive, but don't buy into the old "You can get a decent router for thirty bucks"- that ship has sailed for those of us who use networks for streaming, hand-helds, printers, laptops, thermostats, etc.
As Mark recommended- if the other steps don't work, do a hard reset but save the configuration before you do this.
1) Unplug the AVR's power cord.
2) Reboot the router and if you use a separate modem, re-power them sequentially- modem first, letting it return to normal before re-powering the router.
3) Re-connect the AVR's power cord.
If this works, great. If not, connect the AVR to the router and see if it can acquire an IP address before starting. If it won't/can't, look in the manual for the procedure for doing a network reset. Be warned- some models will only do both in the same procedure, so make notes for the settings.
If you have a laptop, download Inssider and click on the Network button at the top, so you can see how much signal strength you have at the AVR's location, how much traffic is on the channel your router is using and make sure that if you have more than one device providing WiFi, the signals don't overlap and the WiFi network names (SSID) aren't the same. Using the same name is good for roaming, but not when something sits on a desk or a shelf.