R12 PO Security hierarchy

Hi Group

UserXX employee has given position.

This position is added to the PO security hierarchy, above the real buyers positions.

N : Buyers

N+ 1 : Buyer's supervisor, USERXX

N + 2 : General Maanger

Purchase order document type uses Hierarchy as security level.

Problem is that userXX cannot see purchases orders created by buyers.

What would be the problem ?

Regards