I have been trying to configure my Netgear R6400, the DHCP scope and reservations, to setup my home network with some fixed addresses for my pihole and what not. And all I have been getting for quite a long time, is that frustrating error.
Netgear previously told me to wait for a new firmware update and that was an update or two ago and it never fixed it. And a great deal of the fixes such as remove yourself from assignment as the DNS server simply didn’t work for me.
Recently I updated to V184.108.40.206_1.0.41 and when I tried to update the configuration I received this message. Again. So I decided to try three different changes from the first Google search returns. The second one, simply click the setting under Internet Setup for DNS to “Get Automatically from ISP”, let it reboot, make all your DHCP assignments and scope changes and then set it back worked absolutely great.