I had similar case with Nighthawk RS100 Wifi 7 router

I had similar case with Nighthawk RS100 Wifi 7 router.  MyNetgear showed new router registered and armor subscription associated with new router after transferring it on the web site.  However, armor.netgear.com still showed my old router and with no subscription since it was transferred to new router and didn't list new router there.  Fix for me was factory resetting new Nighthawk router with a pin into reset button on back of unit.  Then with a freshly reinstalled Nighthawk app on smartphone, I had to connect to the router's factory SSID with nighthawk app and setup router from scratch with the app.  Apparently the app plays a role in registering existing subscription on router and updating Armor site information so subscription and router are in sync in the setup process.  I didn't use the app to initially setup the router and I set it up manually via the router's web signon screen.  However seems that they are forcing people to use the app which likely does some extra things behind the scenes.