Also let me know if you see following registry entries on that client machine
Go to regedit take reg back up and go to
HKEY_LOCAL_MACHINE\SOFTWARE\Symantec\Symantec Endpoint Protection\SMC\smc_engine_status
If the value of smc_engine_status is "0" that means NTP is Disabled
If the value of smc_engine_status is "1" that means NTP is Enabled
Please check
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Teefer2
If you find teefer2 remove it and reboot the machine
Note making changes to smc engine status ntp enable or disable needs an reboot .
Note:-Please take reg back up before making any changes to it