Hello Agha,
Upgrading to latest version is a two step process, first you will upgrade your Symantec endpoint protection manager, then you upgrade your clients, on your server, open the symantec endpoint protection manager and click on help and support, you will find your SEPM version, to see if clients were upgraded using autoupgrade feature you need to click on the clients tab and on the right side ( client packages) you will see if there are any packages assigned. Liveudpate will not upgrade clients automatically.
I feel that this server rolled back during upgrade process and its on same previous version.
either create a new group and upgrade using auto upgrade or create a new package and install it on the server,
Upgrading Windows clients by using AutoUpgrade in Symantec Endpoint Protection
http://www.symantec.com/business/support/index?page=content&id=HOWTO80780
Create new client installation packages in Endpoint Protection Manager
http://www.symantec.com/business/support/index?page=content&id=TECH102215