Error in Receipt acknowledgement

Hi All,
I am implementing PIP3A8V01_03, In my Initiator Process model i am transforming udm to PIP document and sending to Responder model once Responder model receive the documnet it sends acknowledgement to initiator process model, Here acknowledgemnet is sending to initiator Process i can view in TN Transaction Analysis but in Initiator Process model wait for Ack step is not completing. I hope you understood my problem can any one suggest !