I have an ARRIS SURFboard SB6141 modem. My old set-up is an Apple AirPort Extreme base stationn/router, and my even older set-up is an Apple AirPort Express base station/router. I can easily exchange them, without doing anything to the SURFboard except restarting it. Actually, I'm not sure that I even need to do that. I've never checked.

I just got a tp-link Deco M9 Plus mesh wi-fi system. The set-up seems easy enough, but no matter what I do and what order I reset things, or how long I keep the SURFboard unplugged before I start over, I can never get to the last stage of the set-up and successfully get an external internet connection. Of course the little red light comes on.

The wi-fi network actually is established and I can connect to it from various devices. I can even connect to it and talk to it via http://tplinkdeco.net once I'm on the network, but I really can't do anything significant. I can unplug the tp-link Deco M9 on the fly, and hook the AIrPort Extreme back up, and I'm again good to go.

For whatever reason, I cannot get to the internet with the tp-link connected to the SURFboard.

Any ideas?