unable to view the approvers in approval preview at SRM PO change

Hi,

We are using SRM 5.0,

we are picking approvers from ECC and approvers are picked correctly using BBP_WFL_APPROV_BADI and displayed.

Here the problem is ,  when we change the PO in SRM and check the approval preview before we click order. approval preview is blank and displays as "No approval required".  this is not calling the BADI BBP_WFL_APPROV_BADI when click on approval preview button.

after PO order the approval preview is displayed correctly.

Your help is really appreciated.

Regards

Kumar