I am unable to connect to Nighthawk AX5 AX5400 6 (RAX50v2) admin console, while connected to interne

If I browse to the admin console, IP, I get the login/password prompt. After, entering credentials, correctly, I get a Netgear page indicating 'Access Denied'. However, if I disconnect the Internet connection to the same router, and again try to login, I am successful and can manage the device just fine. So I know my credentials are correct. If, while I am logged into the router, I connect the WAN cable, I am able to continue to work, make changes, etc... But if i logout and attempt to login, I am once again seeing the 'Access Denied'. Note this works this way if my laptop is connected via wired or wireless. No change in behavior. When I first got the router 5+ years ago, I did not have this issue. Ideas?