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 checked your form http://www.jotform.us/form/40586290190152
but I did not find any payment integrations setup on the form.
You need to integrate the form to a Payment Tool for it to have payment integration/link.
Check this user guide http://www.jotform.com/help/165-Setting-Up-Your-First-Order-Form
The field "Pay by Paypal Now" in your form is not associated to any payment integration, so it will not work like the payment tools. It also is not set as a *Required field in your form, meaning form respondent can skip and not answer this question and still submit the form.
Hope this help. Inform us if you need further assistance.