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.
This is something that needs to be configured in your browser.
Unfortunately, I don't know which browser are you using to work with your form. So, I'll share with you this guide: http://www.wikihow.com/Allow-Pop%E2%80%93ups that describes how to enable popups for the most common browsers.
Hope this helps.
Let us know if you need further assistance.