You can perform following steps:
1.Open Symantec Endpoint Protection -- click on Help -- Troubleshooting.
Check for:
-Server name: (It should not be incorrect, offline)
-Group: (It should show appropriate group)
In case if any of the above details are incorrect.
2.Create a Sylink file from SEPM.
-Click the Clients tab in the SEPM and select the group you want.
-Right click on it and select Export Communication Settings.
-Click browse, select a convenient location and name the file "Sylink.xml".
-Click Export.
3. Copy this file to the machine locally.
-Import the sylink.xml within the client by going to Help > Troubleshooting > Click on Import... under Communication Settings.
You can also refer to following links:
-How to change the sylink.xml file in Symantec Endpoint Protection (SEP) 12.1:
http://www.symantec.com/business/support/index?page=content&id=TECH157585