Nighthawk App Logon Error

I'm at my wits end with this app. I have unplugged my router and modem twice now, deleted the app and reinstalled it, I've done just about everything but I can't get past this error. I get to the Login Required page. It's a white page and at the top it says "Log in with your admin credentials to manage your router settings." My user name is admin, I type in my password, which I've changed twice now. It loads for about 3 seconds, and then stops. It then gives me the error "Logon timed out, please try again. If this issue persists, try rebooting your device." Which I've done. Twice. At this point, I have no clue what to do. I have an Apple iPhone XR, my iOS is 15.3.1 and the app version is 2.15.1.2