Domain Name Mapping Not Functioning

I have setup wp multisite on the domain itradelocal.com

I now want to add existing and create new sites to/on the multisite network.

So far now I have created a new site which has the subdomain itradelocal.com/goequestrian All works fine.

I want the domain go-equestrian.com to point to the folder created by wp multisite. I am getting a message when using the Domain Mapping tool 'Domain name is unavailable for access.

I have tried with subdomains activated but encounter the same problem.

That's my problem. I am using Media Temple Grid server with fixed ip address, but is a shared service. MT state that wp multisite with domain mapping should function but the don't support 3rd party apps

I have enabled login for you guys/girls.

Cheer
Chris Johnson