The Symantec Endpoint Protection (SEP) client Web Traffic Redirection (WTR) component fails to forward web traffic request to Web Security Services (WSS). The service may start working if the computer is restarted, or WTR is disabled and re-enabled.
The WTR engine downloads a Proxy Auto-Configuratoin (PAC) file from WSS in order to determine the proxy address it should forward Web requests to. This problem happens when the WTR engine receives a blank PAC file.
This issue has been resolved with WSS Traffic Redirection Engine 18.104.22.168 and later.