Troubleshooting
When updating your registrar with the Cloudflare secondary nameservers (nsXXXX.secondary.cloudflare.com), you get an error.
Upon contacting your registrar, their services confirm that the Cloudflare nameservers cannot be added at this time.
This issue may arise when one of the Cloudflare nameservers used for secondary setup is removed from the Verisign side.
The Cloudflare engineering team needs to be engaged through Support to make sure the nameserver gets registered again manually at Verisign.