Approve PO in EP

Hi, would like to know why the approver not able to perform approve action in role center or EP. In EP no matter at role center or PO form also not able to approve whereas in client’s PO form can.

Moreover the same approver able to perform approve action for Purchase Requisition no matter in EP or client (both role center and PR form)

p/s: already enable approve action for portal in PO workflow.

please advise.

Solved, change to use non-editable PO approval workflow element instead of editable. then approver can approve PO in EP.

Anyone know the reason why? mind to share?