With help from Jeff at Surpass support I've worked out why subdomains didn't work on my site.
They were not working because of a redirect in the .htaccess in public_html. The particular redirect in question was as follows:
Code:
RewriteCond %{HTTP_HOST} .
RewriteCond %{HTTP_HOST} !^robcubbon\.com
RewriteRule (.*) http://robcubbon.com/$1 [R=301,L]
This directs the www to a non-www domain. I read something that said redirecting a www domain name to a non-www domain name, or vice versa, improved SERPs or PageRank.
You can still allow your subdomains to work by excluding them from the redirect. This is done by adding the line
Code:
RewriteCond %{HTTP_HOST} !^subdomain\.robcubbon\.com [NC]
before the RewriteRule. In the above, make sure to replace 'subdomain' with the particular subdomain's name.
So now I know how to make a subdomain whilst keeping my www to non-www redirect.
Still wondering how it is possible to create a duplicate home page in the subdomain...