NextDNS not working on MT6000 v4.7

I've configured the MT6000 to use NextDNS as shown below, but I don't think it's working. NextDNS reports " This device is not using NextDNS. This device is currently using ”Cloudflare” as DNS resolver.

I've confirmed this with https://test.nextdns.io/, which returns "unconfigured", and dnsleaktest.com, which reports that I'm using cloudflare.

A forums search didn't help. Can you provide some guidance?

Please enable "Override DNS Settings of All Clients" as well and make sure that your browser (Firefox does, Chrome does as well, afaik) don't use other DNS servers by default.