Dear All,
The issue is solved. I haven't done anything in SWFWISE or any OBN Configuration.
I have recreated the same issue in Development by removing all authorizations, SAP_ALL, just kept the copied role ZSAP_MANAGER_MSS_NWBC_3 from SAP_MANAGER_MSS_NWBC_3.
By this I got the same OBN Error. Then there were some authorizations missing which I have got from SU53 added into a single role & given to the user.
I have also added the role ZSAP_BC_BMT_WFM_NWBC_END_USER to the user.
Now the issue is solved. Then I downloaded all these roles from PFCG & Uploaded into Production.
Also created the profile & generated the authorizations.
Alas, Thank god. It worked
Thanks all for the help 
.
Namsheed