LEM Agent in DMZ Showing as Non-Agent Node

We have a public web server located in a DMZ. We recently installed the LEM agent on the server and opened the necessary ports in our firewall to allow it to communicate with our LEM appliance on the internal network. While events seem to be being collected and the server is showing up in the list of nodes, it is listed as a non-agent node. Looking for some suggestions as to why it's not showing up with a status of 'connected'. Thanks.