Sub-server on latest version 4.06.gpl GPL not working

I have a domain which is working fine but I'm in the process of developing a new version of the site on it so wanted to create a sub-server e.g. devsite.example.com. This would allow both domains to access the same database whilst working on the new site.

I've created a sub-server on the domain in question and everything looks correct. I've checked the bind file and that has a line in it relating to the new domain which looks correct but the new sub-server isn't responding at all. I've waited 24 hours in case it's a propogation error but it's till not responding.

Any ideas what I might have done wrong ? I'm on an IntoVPS VPS if it makes any difference ....

Thanks in advance