Hi Ram,
Can you double check and confirm that the IDoc has left ECC and was accepted by IDoc adapter of PO? If this is possible, can you reproduce the issue from ECC and collect trace in PO for the corresponding IDoc sender communication channel (using XPI Inspector) or for the whole IDoc adapter application (if XPI Inspector is not available) - in this way, it will be possible to see if IDoc was accepted by IDoc adapter or not.
Can you give a try to find the XI message in Message Monitor of PO, which would correspond to the processed IDoc?
Best regards,
Vadim