For Xantec Shared service server, all Shared SSL Certificates installed on Shared Server Hostname. So need to use the Hostname to access secure services.
To check the server name, please log into the cPanel , it locate on state panel on left side.
Once you have the server name, then you need to use the url as below to acceess
https://*HOSTNAME*.mschosting.com/WHM (for reseller account)
For example, server hostname is KBEXABYTES, so the URL will be as below