I am having the same problem.

I am having the same problem.  If the Pay Pal option is not on the form, and the form is submitted it is shown as a submitted form on the backend of Jotform.  Once I add Pay Pal payment to the form, my payment does show up on Pay Pal as completed but no form information is shown on Jot Form, it is as if nobody filled anything out.  I have their payment and money but no form on Jotform.

I cloned your form (http://www.jotform.ca/form/70335777753263) and add a PayPal Payment field. I did a test submit and it redirects me to PayPal checkout page. However, when I did not complete the payment process,  I checked the Submission page and it was there in the Incomplete Payments.

 

If that happens, perhaps the user of your form did not complete their payment process. Please check this guide to know more about Paypal Incomplete Payments FAQ

 

If you still have problems, please let us know.
Regards

Where can I find the duplicate form? I will try the whole process
...

Here's my clone of your form (https://form.jotform.com/70508558110956). 

You can also clone your own form, please see this guide: How to Clone an Existing Form from a URL.