What is JotForm?
JotForm is a free online form builder which helps you create online forms without writing a single line of code. No sign-up required.
At JotForm, we want to make sure that you’re getting the online form builder help that you need. Our friendly customer support team is available 24/7.
We believe that if one user has a question, there could be more users who may have the same question. This is why many of our support forum threads are public and available to be searched and viewed. If you’d like help immediately, feel free to search for a similar question, or submit your question or concern.
I have tested on a cloned copy of your form and the coupon code discount is effected properly.
Could you try removing the existing coupon, then re-adding it again.
Also clear your browser cache, i have cleared the form cache for your account.
Test and kindly revert back with the changes.