Deactivate an xFi Gateway CGM4140COM

how do I deactivate an xFi Gateway CGM4140COM and get it off the registered devices? I have 2 of them and am trying to take 1 off the network.  It's interfering with the app letting me control the network because it can't see the 1 I unplugged.  My account shows its not responding and it should, I unplugged it, but it will not let me remove it so the network can work together without it.  I plan on returning it placed it on the return pending list.  Now how do I get my system to stop looking for it?