Hi,
Thank you for posting in Symantec community.
I would be glad to answer your query.
Check the following articles:
SEPM Database Backup and Restore fails to run on Win 2008 R2
http://www.symantec.com/docs/TECH161467
Error : "Could not find main class. Program will exit." occurs when trying to open Symantec Endpoint Protection Manager (SEPM) Console
http://www.symantec.com/docs/TECH104766
If not helped,could you please provide the following details to answer your query in more efficient manner.
1) SEPM version details
2) When the backup was taken which you are trying to restore
3) Operating System details