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I'm sorry for the trouble caused to you.
Do you see any error message when you add the iFrame embed code in Prestashop?
Please be noted that you should only add the iFrame embed code and script code should not be added in the CMS page. Please use just the following code and see if it works:
We will wait for your response.
<iframe width="300" height="150" style="width: 100%; height: 687px; border: none;" id="JotFormIFrame" src="//form.jotformeu.com/form/525937729?????" frameborder="0" scrolling="no"></iframe>
use this code instead and change the numbers of the form to yours, it works for me in ps 18.104.22.168
Please share also to us the URL of your prestashop website where we can test the form your form http://www.jotform.me/form/52624359110449
Using the form direct URL does not show the problem.