In last few days we have received numerous tickets saying, "private nameservers you have given doesn't work when i try the update nameserver option". It doesn't work, because you have to register your private namservers with the IP (Given by the tech from us who has setup them on our server). As its solely a domain registrar concern, we are really ignored in most of cases to provide direction how to register them. Basically, After a tech setup them on hosting, remember, you need to register them in your domain control panel, and after that you are able to use those nameservers.
For some popular registrars, here are some directions given on the web by different writers:
Godaddy: http://forum.weborum.com/index.php?showtopic=2697
Namecheap:
1. Login to namecheap2. Click on "Manage Domains"3. Click on your-domain.com4. Look on the left hand side and you will see "Advanced Options"5. Click on "Nameserver Registration"6. Register ns1 / ns27. Click "Add Nameservers"8. Then co go "Transfer DNS to Webhost"9. Add the 2 name servers ns1/ns210. click "Save changes"
11. You're done!
ENOM: http://www.webhostingtalk.com/showthread.php?t=253719
Domainsite: Go to Domainsite control Panel >> Select Domain >> Register Nameserver
Although, if you have registered the domain from someone else, just try to find out the option called "Register Nameserver" in your domain control panel or try contacting your domain support for it. They should be more efficient in solving your issue in this matter rather than us :)