Envoyez ces étapes à votre développeur (en anglais)
Go to whatsmydns.net
Change the search to "CNAME" record
Enter the CNAME record you want to check. If you set up a "www" subdomain, enter "www.sitename.com". If you used another subdomain, enter that subdomain address into the field.
Note: Replace "sitename.com" with your own domain name
Results
Green checkmarks mean that the domain is propagating correctly. Please wait 24-48 hours before contacting your web host.
Red X's in the results means that the domain is not propagating correctly.
A combination of green and red means the domains are still propagating. Please wait 24-48 hours before contacting your web host
Here is a couple of more reasons why you might run through some issues:
1- Your host is just taking some time to update your new CNAME.
2-CNAME is not pointing to custom.clustdoc.com