Suman,
If the FM,ISU_FIKEY_DEFAULT is not able to generate the reconciliation key, then there can be two reasons-
(a) Event 1113 is not activated Or,
(b) The User ID through which the FM is executed is not being maintained in transaction S__KK4_74002323
Check the above two reasons and fix them. Then this FM will be able to generate the reconciliation key.
Hope it helps..
Thanks,
Amlan