Go to your domain name registrar and set the following name servers for your custom domain; make sure to list all four in this order:
ns1.no-ip.com
ns2.no-ip.com
ns3.no-ip.com
ns4.no-ip.com
This will point your domain to No-IP. If you’re using a custom domain on Pro Dynamic DNS or Plus Managed DNS you will need to make this change.
Note: Keep in mind that these are not the DNS servers that you specify in your Internet settings for your computer. Our DNS servers do not perform recursive DNS queries. This means that we do not resolve DNS for domains not managed by No-IP. Please use your ISP’s nameservers for this purpose.