Unable to purchase a domain from eNom

Ok, so I signed up at eNom with [trinitytranslation] and have implemented the Domain Mapping plugin from WPMUDev into my WP Multisite Network.

When I try to purchase a domain from the new website that I have setup on the network [wenxindental], I am seeing this error message;

404 Not Found
The server can not find the requested page:

trinitytranslation.com/wp-admin/admin-ajax.php?action=domainmapping_show_purchase_form&nonce=f2f5a9607e&tld=com&blog=2&success=http%3A%2F%2Fwenxin.trinitytranslation.com%2Fwp-admin%2Ftools.php%3Fpage%3Ddomainmapping&cancel=http%3A%2F%2Fwenxin.trinitytranslation.com%2Fwp-admin%2Ftools.php%3Fpage%3Ddomainmapping%26tab%3Dpurchase%26sld%3Dwenxindental%26tld%3Dcom (port 443)
Please forward this error screen to trinitytranslation.com's WebMaster.

Apache Server at trinitytranslation.com Port 443

Here is some screenshots:

http://note.io/1gyXHtO (domain purchase page)
http://note.io/1g37flY (error page)

Please can you assist me to resolve this issue.