Nighthawk X4S C7800 ability to login and re-config router

Questions:

Can you give guidance how to login to config router? i've been successful in the past but it's always a struggle.  i've read the kb notes and tried 1)loading nighthawk app on my iphone but nighthawkapp error message says router not supported (i confirmed with kb notes the C7800 not listed)  2) www.routerlogin.net and www.routerlogin.com and receive the unsecured  login box to enter router username and password after hitting enter nothing happens and the fields blank out .

Why is it unsecured? this is concerning.  i try use VPN but it chokes. sometimes after multiple attempts i receive a message that asks to reset gateway password (which i dont want) 3) entering into browser 192.168.1.1 .

i've tried these methods on MacBook Air and Dell with VPN on and off. i've tried logging in wired via ethernet .  I started working on the router when my 5 GHZ stopped working yet 2.4 Ghz continued to work.  my goal is to create the most secure router/modem including login to: 1) turn on WPA3 Personal or WPA2/3 Transitonal if avail 2) rename SSIDs for 2.4 and 5 Ghz to same name. TY for any guidance!