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 went ahead and opened your form, I made a test submission. I was redirected to the Paypal payment gateway. So that means the payment integration is properly setup to your form.
Here's a screencast:
If you are receiving completed transactions in your Paypal account BUT in JotForm they are marked as "Incomplete Payment", then it's possible that your IPN is not enabled in your Paypal account. Please see the following guide: http://www.jotform.com/help/276-How-to-Enable-IPN-for-Paypal
Do let us know if that will resolve the problem.