What is an IP lookup?
An IP lookup shows the IP status of your domain and will tell you if your changes to the name server settings have been propagated or not.
If it says "Pending Zone Update" at the top, that means your new name server settings have not propagated through the system yet. You will have to wait for your website to become visible.
If there is a "None" in red in any of the entries for your name servers, that means that name server is online, but does not recognize your domain in its domain list. You need to contact your web host and ask them if your domain has been added to the name servers' domain list.
If there is a red "No response" in any of the entries for your name servers, that means the name server is not even accepting web requests and is probably offline. You need to contact your web host and let them know that your name servers are not online.