BWC-cannot approve PO from GBPA when we have more than one operating unit

Hello experts,

We're on 12.2.12.

We created a GBPA via BWC with two operating units.

When we create a PO from the purchasing responsibility where the GBPA was issued (the same operating unit), it works properly.

However, when we try to create a PO from the same GBPA but from the purchasing responsibility of the other operating unit (which is enabled on the GBPA), an error occurs: 'You cannot create a purchase order because you do not have access to create a purchase order in the selected operating unit.'

Do you have any clue how to resolve this issue?

Thanks,