Hello,
Is the SEPM migrated to the Latest version of SEPM 12.1 RU1?
Good question above.
How are you upgrading these clients? Is that via Migrating and Deployment wizard OR via Autoupgrade?
Are you receiving any error message while migrating?
Could you check if these clients are receiving the packages OR not?
Check the Application logs under Event viewer of the client machines for any installation failure error.
Check the SEP_Inst.log under %temp%, you could upload these logs to us as well.
There are few things which needs to check, preparing clients for migration for 12.1, check the Article below:
Steps to prepare computers to install Symantec Endpoint Protection 12.1 client
http://www.symantec.com/docs/TECH163112
Hope that helps!!