Multiple BG PO Approval

Hi All

We have multiple BG in place, for a PO approval the SCM team is trying to build a position hierarchy. Employee in India BG will raise PO for Singapore BG. However, the requester and approver on the same BG( India). When we try to query the position in Singapore BG we are not able to build the position hierarchy even after HR: Cross business Group is 'Yes'. What is the method or approach for solution. 

Thanks and Regards

Suresh Subramaniyam