NET::ERR_CERT_COMMON_NAME_INVALID After transferring my site from cpanel to ispconfig

Hello..

i recently transferred my website from cpanel (shared hosting)to ispconfig (vps on ubuntu 16.04). everything seems to have gone smothly except that i now get the ssl error screen below, worse thing is that the error screen popsup every single time a page loads.. ssl certificate is enabled on my ispconfig website settings.. please any help trouble shooting and sloving the problem will be very much appreciated as i cant afford let too many customers come across ssl error screen for an ecommerce website... thanks..

Code:

Your connection is not private
Attackers might be trying to steal your information from mydomain.com (for 
example, passwords, messages, or credit cards). Learn more
NET::ERR_CERT_COMMON_NAME_INVALID
 
Automatically send some system information and page content to Google to help detect 
dangerous apps and sites. Privacy policy

This server could not prove that it is mydomain.com; its security certificate is from 
www.mydomain.com. This may be caused by a misconfiguration or an attacker 
intercepting your connection.

Proceed to mydomain.com (unsafe)

 

Error screen says:

But you use it for mydomain.com.

 

nice observation Taleman.. let me try an permanently redirect all traffic to www.mydomain.com to see if will clear the error

 

i simply unchecked ssl on ispconfig website configuration and checked it back after sometime and the error cleared... site is fully secured now..