Hi Ada
Bingo. Though this note was helpful, standard SAP combinations for various fields is setting the field Procurement allowed field in our case for without source of supply. Hence, we need to change this field in input log through a BADI implementation (/SAPAPO/SDP_OPT_LOG).
We are going to give it a try and see if it helps. Thanks for your reply.
Best Regards
Parth Soneji