Import Standard Purchase Orders Program not working in R12.1.1

We are facing a problem in R12.1.1 Conversion for Standard Purchase Orders.

We are submitting the "Import Standard Purchase Orders" program after inserting records to following interface table

  1) po_headers_interface 2) po_lines_interface 3) po_distributions_interface

The program completes without any error but it does not process any records(process_code column values in interface tables are Neither REJECTED nor ACCEPTED). and even there is no errors in po_interface_errors.

Any help on this is highly appreciated

Thanks,

Raju Mantena