On computers with the Symantec Endpoint Protection (SEP) client Web Traffic Redirection (WTR) feature enabled, Internet Explorer is unable to reach any external Web sites, and returns the error message "The proxy server isn't responding". Other browsers may successfully connect to the Web Security Service (WSS).
Enhanced Protected Mode is a feature in Internet Explorer that prevents the browser from connecting to resources hosted on the local computer. If this feature is enabled, the browser will fail to connect to the WTR Local Proxy Service (LPS) hosted on the local computer's loopback interface.
To allow the Internet Explorer browser to connect through the SEP WTR engine, disable the Enhanced Protected Mode configuration for Internet Explorer.
Disable IE Enhanced Protected Mode
Open Internet Explorer
Click the gear icon > Internet Options, select Advanced, and uncheck Enable Enhanced Protected Mode and Click OK to save the settings
Restart the computer to ensure the settings take effect
Note: This setting can also be enabled through Windows Group Policy. If the affected computers have a Group Policy Object (GPO) configuration that enables IE Enhanced Protected Mode, ensure this GPO is removed from the affected computers.