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 just have tested your form in a phone emulator, tested using an iPhone 6 Plus device and the form is showing fine, the submit button is there:
Could you please confirm us that the issue is still there?
If so, I would suggest you to add the mobile responsive widget: https://widgets.jotform.com/widget/mobile_responsive
This guide should help you to add the widget to your form: How-to-Add-a-Widget-to-your-Form
Although our forms are responsive by default, this should help you to display it responsively too, please let us know how it goes.