Hi Archana,
use the table /AIF/STD_IDX_TBL to find the message log , you have to enable the AIF configuration under error handling to select the message from above mentioned table .
you can use the append structure to store the message value in table /AIF/STD_IDX_TBL and same will be used as selection screen values in /n/aif/err transaction.
1) use SU53 to find the authorization issue
2) check the above table with SXMB_MONI message GUID .
3) check the inbound queue logs
4) Are you capturing/passing the application system(RFC/BAPI/Call Transaction) exception to AIF Function module?
Regards
Sukumar