The DNS must be correctly pointing to the hosting account. Whether the domain is being pointed by name servers or A records, the DNS must be exact and have been changed from the correct DNS host file, or the site may not propagate correctly or at all. For name servers, ensure that these are changed at the domain’s registrar. A records must be changed whenever the domain’s host file is located.
For more information on changing the DNS for a site, please refer to the following articles:
Changing Name Servers (or DNS)
How to Point My Domain to HostGator When Using DNS Elsewhere
Remember: It takes up to 48 hours from the time name servers are set before working consistently.