A sequential power cycle is the first step in clearing connection problems such as the error code says you have, and the order and timing of the steps is important to success:
1) turn off the Xbox and unplug the power supply cord from the back of the Xbox then 2) unplug power from the router (Some folks have a combination modem-router AKA 'gateway' or only use a modem with no router. If either, skip steps 3 & 6). 3) unplug power from the modem. 4) Wait at least 5 minutes then replug the modem/gateway power. 5) Wait 'til the light on the front of the modem/gateway which says BROADBAND, ONLINE, READY, CABLE or DSL is on solid (not flashing), then plug in the router. If you have a gateway instead of a modem and router or a modem with no
router, then when that light says it's ready, skip to step 7. 6) Wait until the WiFi light on the router is on; you may not use WiFi, but it's still a good indicator your router is finished booting up.
7) Plug in and turn on the Xbox.