RAX40 can't connect to internet using wan port

I am trying to install a new RAX40 Nighthawk to handle wifi in my house rather than the Pace 5168N-110 (a modem/router) supplied by my ISP.  I have followed the directions (many, many times) in the Nighthawk app. I had my ISP configure the Pace modem, turned off the radio in the Pace etc (in fact, the ISP replaced the old Pace modem I had with this one after they couldn't configure the old Pace modem to work with the RAX40).  When I connect the RAX40 to the Pace via the WAN port, the app will say that the cables are connected but there is no internet connection via wifi.  I can get wifi through the RAX40, though, if I connect to it to the Pace through one of the LAN ports.  But then, the app says I am not connected to the netgear wifi network - even though I am and am able to access the internet.  And not just my phone; others in my household are able to access the netgear wifi network and have internet access as well. But connecting this way (via LAN) means I can't use the app on the phone at all. Does this seem right? I don't understand why I can't use the device the way Netgear says it is supposed to be configured.