WF Notification Approval APIs

Hi 

We have a requirements to provide APIs allows to approve WF Notification (PO/REQ/AP INVOICE).
I used WF_NOTIFICATION.SETATTRTEXT and  WF_NOTIFICATION.RESPOND  it's working fine against POs. 

For requisition, I used the same APIs, it worked successfully but still have a problem which is comment is missing, i.e. comments provided in API not exists in approval action history. Any idea how to fix it ?    

for AP INVOICES notification is not working any advice how to figure out this issue ? 
kindly note that AP INVOICES using AME approval. 

Your assistance is much appreciated, please note that we're using Oracle r12.2.6.