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.
May I know what embed code you are using?
Have you tried following this guide: http://www.jotform.com/help/37-Adding-Form-to-Squarespace? It might be quite outdated but the steps should still be the same. As mentioned in the guide, you need to use the iFrame embed code, but make sure to remove the <script> tag.
If your website is already published, you can share the website link to us so that we can check it.