Symantec Endpoint Protection (SEP) client configured to use the same proxy settings as configured in Internet Settings. However, when a proxy is removed from Internet Settings the SEP client is still trying to connect to it.  

Rebooting the machine may fix the issue.

Log.lue shows that the LiveUpdate session fails with:

Server selection failed for server HTTPS://liveupdate.symantecliveupdate.com/ on port 443.
Proxy (proxy IP/URL) is configured for server (liveupdate.symantecliveupdate.com). Won't go for explicit DNS query.

Download Error for minitri.flg. SERVER DOES NOT EXIST or some network issue.
Proxy connect error while downloading minitri.flg. UNABLE TO CONNECT TO PROXY.

For 14.3 clients, a setting is stuck on the client, forcing it to try and use proxy settings when the server policy isn't configured that way.

To resolve the issue, import the current sylink.xml policy for that server. See this article for more information: How do I replace the client-server communications file on the client computer?

This issue is fixed in Symantec Endpoint Protection 14.2 RU2. For information on how to obtain the latest build of Symantec Endpoint Protection, see Download the latest version of Symantec software here.