Please be patient after changing Domain Name Server (DNS) Settings. The settings can take up to 72 hours to propagate throughout the Internet.

We searched Google for “Domain setups can take up to 72 hours depending on propagation.” which was in an email message that our web hosts had sent us previously. We found many similar items confirming the 72 hour wait, including the one below:

About Domain Propagation
(Quoted below from https://help.fasthosts.co.uk/app/answers/detail/a_id/1/~/domain-propagation )

Why do I have to wait 72 hours for changes to my domain to take effect?

When you register or update a domain it can take up to 72 hours for all the computers on the Internet to notice these changes. This is called DNS propagation and is a property of the Internet. This period will be the same whoever you register or modify your domain name with.

Each domain name has its own records that tell other internet users where certain services are held (website, email etc).

When you visit a domain your Internet Service Provider (ISP) will look up the domains records and provide your computer with the relevant information.

To save time, once an ISP has looked up a domain, they'll store this information for a few hours. If another customer of the same ISP browses to this domain name the ISP will provide the same details that it saved the first time it looked.

Typically, ISP's will store this information for between 24 and 72 hours before looking up fresh domain information again.  So if you make any changes to your domains DNS record it can take up to 72 hours for an ISP to look up your domain name again and notice the changes you made.