Web browsers present an error page stating "The Specified Client-ID Agent session does not exist" when Symantec Endpoint Protection (SEP) Web Traffic Redirection (WTR) is enabled.
The error page shown in the browser:
Your credentials could not be authenticated: "The specified Client-ID Agent session does not exist.". You will not be permitted access until your credentials can be verified.
The is typically caused by an incorrect username and/or password, but could also be caused by network problems.
Tech support information: authentication_failed more
For assistance, contact your network support team.
This problem can happen when a computer rapidly switches between WSS datacenters. When this switch happens rapidly enough, the SEP client may send an authentication token from one datacenter to another datacenter, which will not be able to authenticate the session as authentications aren't shared between datacenters.
Modify the PAC files used by affected clients to point to sep-wtr.threatpulse.net instead of proxy.threatpulse.net