Sometimes registering your custom nameservers is not enough, especially if you are using private DNS.
In those cases, you need to create glue records. These glue records will point each nameserver to the IP addresses permanently. To do this from within your Name.com account, you will need to first point your domain to use our default nameservers, then create an A record for each server. In the Host section of the record, add the nameserver’s prefix (such as ns1), and in the Answer section put the IP address of the nameserver.
Once you see the correct IP addresses come up when you ping these nameservers, you'll know that the records have correctly registered. This usually takes about 24 hours. Once the nameservers are registered, you can use them on any domain names you wish.