"The receipt is missing a cost" for PO Receipt transactions in periodic costing

Hello,

I have an urgent issue please,

We are having 6 "Not processed" costing status transactions after running create cost accounting distribution.

These transactions are PO receipt and one return. WHat is the cause of these "Not processed transactions"?

We are using periodic acerage cost method.

One note: these items have already costed transactions, not all are "Not processed".