SSL on sub-server not working

I have a domain ‘’ and a subdomain ‘

Virtual Sub-Server
In domain

Parent virtual server

I have created a certificate :
Web server hostname Issuer name COMODO RSA Domain Validation Secure Server CA
Issuer organization COMODO CA Limited Expiry date May 27 23:59:59 2018 GMT
Certificate type Signed by CA

somehow I don’t think https is working for the site. any ideas what else I need to setup ? doesn’t show any secure icon.

thanks for any pointers