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 am not sure what might have caused this issue for you, but it seems like your current theme wasn't properly applied when you've first tried applying it.
Please try going to Setup & Embed > Themes, and selecting another theme - it can be any theme really. After you have selected that other theme, click Save to apply it, and Close the themes.
Then, click Preview to preview the form with your new theme. Is it applied on the Preview?
If this other theme was applied successfully, please go to Setup & Embed > Themes again, and select your desired theme.
Click Save to save this theme, and then Close. When you click Preview again, is your desired theme loading?
Please try it out and let us know how it goes.
I am having the same problem. I can apply another theme, but when I go back and re-apply my created theme, it shows in the theme window, but when you preview, it has no theme at all.
https://form.jotform.com/53075343202142 with GSDH theme
Your question is moved to a separate thread and shall be addressed there shortly.