Hmm... that AC1900 isn't a Modem or Gateway, it's just a router (and a very nice one at that!) that plugs in to your Modem or Gateway. Did your XFINITY Home service connect through a Netgear WNR1000 before? If so, then you would connect the WNR1000 to a port on your AC1900 and things should be back to normal with your XFINITY Home...
