On the Libraries tab in the Management task area, click Inventory library in order to run inventory. If enabled, select the ...

1. On the Libraries tab in the Management task area, click Inventory library in order to run inventory. If enabled, select the option to run Fast inventory, otherwise run Detailed inventory. This will update the library state as seen by DPM. 
 2. Retry your failed operation after DPM has completed the inventory successfully.