I recently upgraded a Windows server to the latest version of Symantec Endpoint Protection and the server was no longer accessible on the network after the upgrade. The server would not respond to network requests even though the console was working. It turned out the full SEP feature set was installed, including the SEP firewall. Additionally, now the firewall policy was applied to the server. This caused the SEP firewall to isolate the server from the network.
To fix the problem I uninstalled Enpoint Protection and reinstalled without the firewall feature set. I also applied a firewall policy just in case the firewall feature was installed on that server again. My suggestion is to modify the SEP installation document, so that a firewall policy is not applied.