Connecting Nighthawk App to ac2200, EX7300v2

I reside in a very rural area with limited internet options.  I’m currently using a Netgear AT&T MR6500 for internet access and have 3 - Netgear AC2200, EX 7300v2 extending the signal through the house.  Occasionally I have issues with 2.4 band.  I wanted to use the nighthawk app to access my ac2200 extenders but the app requires me to log into the router, MR6500.  However, the app doesn’t accept my MR6500 password.  Does this mean the nighthawk app doesn’t recognize the Netgear MR6500 as my router?  Thanks in advance for any help!