Have you ever wondered what this little arrows mean next to the Last Seen time? Green means that your device is "Active" and red means that your device is "Inactive". So what does this mean, Active or Inactive?
Normally a device needs to "phone home" every once in a while to check for Compliance, to update the App Store, etc. This communication is called the Heartbeat and the last time a device has "phoned home" is shown as the Last Seen time.
Now, if a device misses Heartbeats because it's switched off, doesn't have phone coverage or because the device is not enrolled anymore (someone disabled the agent), then eventually the device gets the Inactive or Down state, the red arrow-down. Thismeout. threshold is called the Device Inactivity Timeout.
You can configure both the Heartbeat Interval time and the Device Inactivity timeout.
The Heartbeat Interval timeout can be found in the System Settings under Device / <platform> / Agent Settings.
The Device Inactivity timeout setting can be found in the System Settings under Device / General / Advanced.