If the error shows that they are not using the correct name servers:
1) go into the terminal and type in
whois <their site name>
and if they are pointed at our nameservers:
ns1.rgnameserver.com
ns2.rgnameserver.com
ns3.rgnameserver.com
ns4.rgnameserver.com
1.5) You can try move on to sync their dns in mcp. Also sync their dns in the email drip by going to https://drip.realgeeks.com.
2) Click on "Companies" in the top navigation.
3) Search for the site.
4) Click the DNS button to the right of their site and then they should be all set!