Thank you for reaching out to Jotform Support. Please note that on the payment fields, only one coupon code can be applied however, there is a workaround to add the products outside the payment fields along with the coupon codes and then pass on the total amount to the payment field. Here is a guide on how to do it.
In case I misunderstood you, please provide us with the Form URL and a more detailed explanation of your requirement to assist you further. If you need further assistance, please let us know.