So some of these TLDs will not allow you to change Name Servers until they can verify that the NS you are trying to switch to are responding authoritatively for the domain. One way to test with Cloudflare that we are doing that is to query your Cloudflare NS using a command line tool like
🚨 $ dig cartus.is @xxxx.ns.cloudflare.com SOA +short
yyyy.ns.cloudflare.com. dns.cloudflare.com. 2037585854 10000 2400 604800 3600
You can also use online tools like this:
xxxx.ns.cloudflare.com with one of your assigned Cloudflare NS and in the SOA record response you should see one of your assigned Cloudflare NS in the
yyyy.ns.cloudflare.com part. As long as the domain is “Pending” in your Cloudflare account, you should see a good SOA response like the above one.
If you don’t see that - let us know. If you do - then you need to talk to your domain registrar about why they are rejecting the NS change.