Dear All,
I am able to find the reasons for this issue. I've seen some SDN threads raised for same issue but there was no conclusion about the solution.
Finally, the reason I found is due to missing attribute in PPOMA_BBP 'SYS',(system alias) in order to allow professional purchaser to confirm goods via central role / through POWL (by selecting SC and then with reference to confirmation) attribture 'sys' (system alias) needs to be maintained for those users.
Hope this information will help for those who face this issue in future.
Regards,
Govardhan