cannot map domain to subdomain

I have installed the Domain Mapping plugin, moved sunrise.php and added the define( 'SUNRISE', 'on' ); line in wp-config.

My network install is in a folder in a VPS account with westhost. The network install is in idxmlspress.com which is an add-on domain setup with wildcard subdomains enabled.

My primary domain is chrissmithcio.com. The IP address for my VPS is 69.36.185.50 and the name servers are SNS1.WESTSERVERS.NET and SNS2.WESTSERVERS.NET.

I am ready to take my first client site live. The subdomain is caferealtyny.idxmlspress.com and I want to use the URL caferealtyny.com to access the site.

The domain is registered at godaddy I have access to account.

When I go to Settings > Domain Mapping > Mapped Domains I get No Items found and there is no option to add a domain.

What steps remain in order for me to map the domain with this plugin?

Thanks