API AR Transaction can't create invoice

Dear All,

I need your solution for my problem, i already create source code for create invoice AR Transaction but when i executed, i always getting error like this "UNIQUE ALWAYS USED"

this is my code :

CREATE OR REPLACE PROCEDURE APPS.TT_AR_TRANSACTIONS(

                            ar_order_number   IN NUMBER,

                            ar_trx_number     IN VARCHAR2

                            ) AUTHID CURRENT_USER IS

  

    ar_header_id            number;

    ar_bill_to_customer_id  number;

    ar_bill_to_site_use_id  number;

    ar_cust_trx_type_id     number;

    ar_id_header            number;

    ar_id_line              number;

    l_return_status         varchar2(1);

    l_msg_count             number;

    l_msg_data              varchar2(2000);