Hi Prasath,
Can you please check the couple of below suggestions and advise
1.) Check whether this program is running in your system - CLEAN_REQREQ_UP & BBP_GET_STATUS_2
2.) If it is running, please check whether the confirmation status is "Posted in the backend"
3.) If the confirmation status is "Posted in the backend", Please assign the SAP_ALL profile to the user and try to do the Return Delivery.
4.) If you are able to do the Return Delivery after assigning the profile, then there is a concern with the authorization object.
The Authorization object is BBP_PD_CNF (SRM: Confirmation in EBP) and the field name is ACTVT. Please check this link for your reference.
Kindly revert if you need any further info.
Best Regards,
Bharathi