According to your inquiry, it seems that the paying bank refused to pay you. In other words, the letter of credit, which is considered as the safest payment method, is not insured. Maybe this is a bank with average credit. Can you send me your name? You can use it as a reference. It also reminds the seller to check the credit status of the issuing bank when accepting the foreign letter of credit.
In addition, this matter should really be discussed with the bank. Is it possible to go through legal procedures in this case?