After installing new DLP Endpoint Agents, and confirming via the agent logs that the agents are checking into the Endpoint Server(s), the agents are not showing up in the Agent List in the Enforce Console.
Any DLP version
There are outdated agent configurations that have not been applied to agent groups in the DLP Enforce Console when the Endpoint agents tried to check-in for the first time.
Login to the Enforce Console and navigate to the System -> Agents -> Agent Groups page. Check the boxes by any agent groups that have an outdated agent configuration and click the Update Configuration button. Click OK to confirm in the Update Configuration dialog box. Finally, restart the "Symantec DLP Detection Server Controller Service" on the Enforce server and monitor the agents to verify they are now visible in the Enforce Console.