App says XB8 Gateway is not compatible with Pro WiFi Extender

I just upgraded my service to the 2 Gbps plan and was offered an XB8 and Pro WiFi Extender as part of the promotion. The gateway activated just fine, but when I attempt to setup the extender, the app says my gateway isn't compatible. I spent an hour doing tech support chat yesterday, which obviously didn't help. The tech said he could see a failed activation. He also said he was updating some settings on the gateway and to give it an hour then reboot the device. Needless to say I have rebooted (power cycled) multiple times yesterday / today and it has not helped. The app still says the gateway isn't compatible.

Any suggestions on what to try next? For now, I have the extender sitting right next to the gateway. They are not cabled together, just sitting next to each other. The light on the extender flashes, as if it is eager to be put to work.