FI311, No commitment item entered in item 00010 1000

Dear experts:

when i create a purchase order, which copied from a purchase requistion, then system has following errors: message no: Fi311 No commitment item entered in item 00010 1000.

then i check each item of the purchase order, and use the transaction code FMDERIVER test the deriver rule of commitment item and fund center, every item of the purchase order has right commitment item and fund center. what is the reason!

Best regards!

Wayne.xie