Unable to generate Credit Memo while using API

Hi Team,

I am trying to create a credit memo using API but its throwing the error:

Failure encountered in AR_CREDIT_MEMO_API_PUB.Create_request call to arw_cmreq_cover.ar_request_cm

Below is the API:

set serveroutput on size 1000000

DECLARE l_dummy varchar2(240); 

  l_customer_trx_id ra_customer_trx.customer_trx_id%TYPE;

  l_line_credits_flag ra_cm_requests.line_credits_flag%TYPE;

  l_line_amount NUMBER;

  l_freight_amount NUMBER := 0;

  l_cm_lines_tbl arw_cmreq_cover.cm_line_tbl_type_cover;

  l_cm_reason_code VARCHAR2(150);

  l_comments VARCHAR2(150);

  l_msg_count NUMBER := 0;