Mass Addtions -Unable to do Unmerge

Hi,

We interfaced supplier invoices from PA module  and  the invoices  interfaced as merged 

As per Doc ID 1252144.1

13. How to unmerge all mass additions lines attached to a parent line ?

A.

Below navigation should be followed to unmerge the mass additions lines which are merged earlier.
Navigation is

Mass Additions > Prepare Mass Additions Form.
Query the Mass Addition for the transaction.
Choose the Merged Parent that you want to undo.
Click the Merge Button.
At this point you can either individually uncheck the lines or select the Special/Unmerge All.

It does not work , we do not see the lines. Please see attachment.