CURL error and Domain Sale Errors

An order has received its first payment but the automatic provisioning has failed and requires you to manually check & resolve.
Error: CURL Error: 7 - couldn't connect to host (IP: 67.***.*.*** & 67.***.**.**)

That's what I get when a client tries to order a domain from me. Please let me know how to fix this, I am using WHMCS, WHM/Cpanel and the server is a VPS.

Thanks,

T