While configuring the Threat Defence for Active Directory [TDAD] unable to add an Active Directory Getway [ADG] agent
Symantec Endpoint Security Complete managed Symantec Endpoint Protection 14.3 RU6 client and Symantec Data Center Security Server Agent [DCS]
From ProcMon shows that the PCHSetupRunner.exe cannot find the ccLib.dll. it looks like the DCS agent provides its isolate.ini that conflicts with SEP isolate.ini according to the paths that ccLib.dll is looking for.
The fix is targeted for SEP 14.3 RU9 client.
Copy C:\ProgramData\Symantec\Symantec Endpoint Protection\14.3.8268.5000.105\isolate.ini and C:\Program Files\Symantec\Symantec Endpoint Protection\14.3.x.x.x\Bin64\ccLib.dll to C:\Windows\system32
Note: Once the ADG is configured successfully delete the files isolate.ini and ccLib.dll copied to C:\Windows\system32