Purchase org is empty in MRP PR

dear all

i created 1 PIR for 1 material code, 1 vendor code under 1 plant and 1 purchase org, but 2 categorys, both standard and subcontract. Source list maintain correct, quota arrangement created with 2 items, "F" and "F+L", same vendor code, different percentage.

After MRP run, PR generated refer the quota arrangement, all data in standard PR are correct, but purchase org is blank in subcon PR, appreciate if any expert could explain it or figure out anything data maintenance is wrong,thanks.