JotForm is a free online form builder which helps you create online forms without writing a single line of code. No sign-up required.
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 because you have enabled the "Unique Submission" option in your "Form Limits".
You have set it to "Loose Check", this means if the users are using the same browser, they won't be able to make multiple submissions. Unless they clear their browser's cache or cookies. You can disable that option is you are not limiting your form submissions. Please refer to this guide to learn more about that feature: http://www.jotform.com/help/64-How-to-Set-Unique-Submissions-on-a-Form
Let us know if you need further assistance on this.