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.
I currently could not reproduce this issue though. No other users have reported similar problem so far as of today also.
It is possible that it was just a temporary hiccup due to network/internet connection lag.
Can you please retry again? Try also with other browser, like Chrome or Firefox.
I already test on my end using your form http://www.jotform.co/form/52672556055863 and the Form Designer loads just fine.
Hope this help. Let us know if the issue remains.