Using a Pre-Owned 2WIRE 3801HGV Gateway

I recently was given an AT&T U-Verse 2Wire 3801HGV Gateway from a friend who moved and wasn't going to be needing. It works fine, since I'd used it multiple times at his house, and never had problems. A few months back after obtaining the gateway, I moved back home where they have ATT Dsl with the little motorola modem. It's slow as crap and the cisco router ATT sent with it is absolutely terrible and continually shuts off for no reason. After dealing with this for a few months I decided to pull out the gateway I was given and plug it in, but it doesn't want to get internet connection at all. Everything is plugged in, all the lights come on, except the Broadband light, which flashes green, then flashes red and continually alternates back and forth between flashing red and flashing green. All my cables are brand new and in perfect working order. Is there anything, anyone can tell me so I can get back to having a fast AND stable connection? Cause if this keeps up, I'm just going to cancel my DSL and find someone else, even if it costs me more.