PLS-00905 : object APPS.PO_CORE_S is invalid

complied these invalid objects.
SQL> select owner,object_name,object_type,status from dba_objects where object_name='PO_CORE_S';
OWNER    OBJECT_NAME    OBJECT_TYPE     STATUS
----------------------------------------------------
APPS        PO_CORE_S           PACKAGE              VALID
APPS PO_CORE_S        PACKAGE BODY      VALID
APPS PO_CORE_S        SYNONYM                VALID