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JotForm is a free online form builder which helps you create online forms without writing a single line of code. No sign-up required.
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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.
Upon checking your form, I found that you have "Unique Submission" set as "Loose check". This is actually preventing user to send multiple submission from the same computer.
Here are the steps to change it (allow multiple submissions):
1. Load your form in editor.
2. Click on "Setup & Embed" and then "Preferences"
3. In the preferences window, click on "Form Limits" tab.
4. Change the "Unique submission" value to "No Check" from the dropdown to allow multiple submissions:
Hope this helps.