DPM automatically refreshes protection agents every 30 minutes on servers that are continuously connected to the network. You can manually refresh the agents in the Management task area.
To manually refresh the protection agent status
In the Management task area, click the Agents tab, select the computer, and then in the Actions pane, click Refresh information.
For client computers that are not continuously connected to the network, DPM will not automatically refresh the agents every 30 minutes. In the Management task area, on the Agents tab, the status will appear as Unknown until you manually refresh the agent status.