The reason why this error could occur is due to DPM not being able to access the DPMDB. The reason why is endless and this is DPM’s way of saying that the communication to the DPMDB is lost.
The way to fix this is however simple! Open the DPM Management Shell and run the DPMSYNC command with the switch -SYNC. This will verify the DPMDB with the protected objects and make “adjustments” so you will be able to access your DPM server again. When the command is done you can access your DPM console (meaning that the DPMDB is now accessible) and ALL of your protected items will be in the same state….Replica Inconsistent.
Simply run a Consistency Check on your protected items and you will soon be back on track!