Hello,
Have you tried working on these Steps provided below: (Try considering these steps below to Block the Traffic of an Application)
Best Practices Guide to Application Learning in Symantec Endpoint Protection Manager (SEPM)
http://www.symantec.com/business/support/index?page=content&id=TECH134367
How to set up learned applications in the Symantec Endpoint Protection Manager
http://www.symantec.com/business/support/index?page=content&id=TECH102994
You can set the default policy when Endpoint Protection detects changes in an executable. Choose between Ask, Block the Traffic, or Allow and Log.