NBR750 Orbi AX4200 5G - App not acknowledging new email address

I recently got an Orbi NRB750 5G router and satellite from someone who had only needed it as a stop-gap. He changed the registration email address to mine and it all shows up perfectly under my account on the Netgear website.

However, when I try to go into the Security settings on the Orbi app, I get the message, "Your router is registered to [old email address]. Login using this account and try again."

I've rebooted the router and restarted the app, but this does not change.

I need the app to acknowledge the change of registration email - does anyone know how to make this happen?

Thanks