iPhone Nighthawk App sends security code to retired iphone & sends code via email that never arrives

My Netgear Nighthawk 9000 router is up-to-date and functional.  I have been accessing the settings fields using routerlogin address via MS Edge.  I installed the Nighthawk iPhone app on my iPhone 12 and signed in using my login and password.  The app responded with a request to send a security code because it didn't recognize my iPhone.  It sent the code to my retired iPhone.  Retries brought the same outcome.  Next, I tried the alternate method of sending the code via email.  The app had my correct email address, but the code never arrived.  Retries brought the same outcome.  How does this get resolved?  Thanks!