HI,
Check this
Symantec Endpoint Protection Manager 12.1 Communication Troubleshooting
http://www.symantec.com/business/support/index?page=content&id=TECH160964
Try to one client
Check in the registry (HKEY_USERS\.DEFAULT\Software\Microsoft\Windows\CurrentVersion\Internet Settings) those keys
"ProxyEnable"=dword:00000001
"ProxyServer"="test:80"
2. Change ProxyEnable to 0
3. Delete ProxyServer key
These settings are also cached in Hex format in the following location: HKU\.DEFAULT\Software\Microsoft\Windows\CurrentVersion\Internet Settings\Connections
-DefaultConnectionSettings
-SavedLegacySettings
If DefaultConnectionSettings and SavedLegacySettings are present, they will re-populate the proxy settings. If they are NOT present, they will be generated with the current proxy settings. This can cause issues if the customer tries to alter just "HKU\.DEFAULT\Software\Microsoft\Windows\CurrentVersion\Internet Settings\ProxyEnable" without also purging DefaultConnectionSettings/SavedLegacySettings before a reboot.