Source:  NDPSM.NLM

Possible Cause:  This error may simply be the result of a typing mistake made by the user at the command line. It could also occur if the eDirectory volume object associated with the NDPS Manager has been deleted, in which case eDirectory will change the NDPS Manager to an "unknown object."

Action:  Make sure you have typed the command correctly. If this is not the problem and the volume has been deleted, you will need to associate an NDPS Manager with an existing volume and re-create the printers that were assigned to it.