Hello,
I am not sure on how are you moving the SEPM 11.x to a new VM machine.
You may like to check this Article:
How to move the Symantec Endpoint Protection Manager server to a new VM or server machine with a different IP.
http://www.symantec.com/docs/TECH95311
Once the succesful movement is done to the Latest VM machine, you may follow the Best Practices to upgrade to SEPM 12.1 -
Best practices for upgrading to Symantec Endpoint Protection 12.1.2
http://www.symantec.com/docs/TECH163700
Once, the Migration is done to the Latest SEPM 12.1.2, you may like to check these Best Practices -
Best practices for virtualization with Symantec Endpoint Protection 12.1.2
http://www.symantec.com/docs/TECH197344
Symantec Endpoint Protection 12.1 & Virtualization
http://www.symantec.com/docs/TECH194383
Does Symantec Endpoint Protection 12.1 support VMWare vShield?
http://www.symantec.com/docs/TECH175568
Hope that helps!!