If there was a previous version of Norton Internet Security (NIS) installed on a Mac OSX machine and it was uninstalled through the Graphical User Interface (GUI), then this issue will occur upon installing the Symantec Endpoint Protection Cloud (SEPC) client.
Mac OSX 10.6 - 10.12.1
No error message is displayed, however, the previous NIS agent will appear to be running in place of the SEPC agent and the windows will all depict the previous agent.
There are left over configuration files from the previous NIS agent installation and need to be completely removed before attempting to install the SEPC agent.
Follow the steps and run the attached script from the following article:
(Removing all Norton programs for Mac by using the RemoveSymantecMacFiles removal utility)