Do the following activity on client and Sepm serve machines:-
On SEPM server machine:-
1. Login SEPM server console.
2. Go to client tab.
3. Right click on any one group and export the Sylink.xml file and save on any location.And take sylink.xml file on pen drive.
On SEP client machine:-
1. Go to start and click on Run.
2. Type the command (smc -stop) to stop the SEP client service.
3. If you are define the service stop password please type the password.
4. Go to C:\Program Files\Symantec\Symantec Endpoint Protection
5. Paste the server exported Sylink.xml file on location and replace with old one.
6. Go to start and click on Run.
7. Type the command (smc -start) to start the SEP client service.
Then check the client online status ..your client should be online.