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.
I've tried accessing the Embed Form wizard on a Firefox browser v40 and it seems to be working fine at my end.
Please try updating the Flash plugin to the latest version and see if that helps. Also, please refer to the following guide from Mozilla that can help you with this issue.
Please let us know if you need any further assistance. We will be happy to help.