wifi calling will not connect after installing Orbi

I installed a Netgear DM200 VDSL modem and an Orbi router and 2 satellites two days ago, replacing an AC1900 Nighthawk modem/router.  I'm on router firmware version V1.9.1.6

This relates to wifi calling using a Samsung Galaxy S7 android phone.  My phone returns a message of REG99 - Unable to connect when I try to turn on wifi calling.

Wifi calling worked with the Nighthawk but does not work with the Orbi even though my phone has a wifi connection and I can browse the internet with it using wifi.  I contacted Netgear support and was blown off; the tech said that if the wifi was wortking for other devices that it would work for wifi calling and said I needed to contact Samsung.  I pointed out that the only new components in the system were the modem and Orbi, but he refused to consider the possibility that one or the other was the problem.

I've contacted Samsung (did some maintenance and a reset - no change); T-Mobile, my phone carrier (blamed the ISP - must have thought I was using their modem/router); and CenturyLink (they delivered internet to the modem and stopped there).

I'm within 3 feet of the router when trying to use my phone for wifi calling.

I need wifi calling for my basement office. Help and advice are greatly appreciated.