Neha,
To confirm if the certificate is correct, from the device while outside the network/DMZ. If you open your web browser and enter the same url you are using on the client you should get the I am here! message without any certificate warnings or errors. If that is successful you know two things. First that the hostname for the virtual IP you created correctly resolves to the sever and second that the certificate the DMZ is presenting matches what you installed on the client.
https://{Virtual IP hostname}:8081/sub-url
If this is successful then you will need to look at the client install.
The error I see in your screenshot indicates a communications error 14 which is most often a problem with the routing or network connection between the client and the server or that the server is not running. Please verify with the URL in a browser and see what you get back as the first step.
--Bill