You go to create a subdomain and get the following errors.

[stextbox id=”warning”]There was a problem creating the sub-domain: You do not have permission to create subdomains of the server’s hostname[/stextbox]

Or
[stextbox id=”warning”]The system experienced a problem during the creation of the “example” subdomain.[/stextbox]

This was fixed by changing settings in WHM: WHM Home -> Server Configuration -> Tweak Settings

Allow users to park subdomains of the server’s hostname: ON