R6400v2 Nighthawk app on new cell phone problem

I have a model Netgear R6400v2 wifi router. I bought a new cell phone and downloaded the nighthawk app to it. I cannot get the Nighthawk app to conect to my Netgear router using the new cell phone. It keeps asking for a password for the admin user. I set up a new Netgear account thining that would help.  When I click on the app on the new phone it brings me to the nighthawk admin screen asking for the password.  How do I get the Nighthawk app to connect to my Netgear R6400 wifi router on my new phone?