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.
It would depend on what type of Paypal you are using. I've cloned your form and I see that you are using the standard Paypal checkout. In the description it says that you will need to have a Business or Premiere Paypal account, you can log in to your Paypal account to see if you have the same account type.
If the problem is not in the account type, you may try re-adding the Payment tool again and clearing your form's cache. See if that fixes the problem.