It will show as unmanaged until the agent polls in for the first time. Have you confirmed on the target system that the agent has deployed successfully (you should see the framework service running)? If so, issue a wake-up call from ePO, or from the McAfee Agent Monitor on the managed system, select 'Collect and Send Props'. If the agent successfully communicates back, it should show as managed. Also check for potential duplicate system names (in System Tree select 'My Organisation', show 'this group and all subgroups' and search for system name).
Let me know if you need any assistance with anything mentioned above.
Moved to ePO for clarity.