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.
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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 have tested your form https://www.jotform.com/70127995623159 on my Samsung Galaxy S4 and I saw that calendar of Large Date Picker is not fully responsive.
On my cloned form I was able to resolve the issue by checking Make This Form Responsive option inside of Form Designer.
Please try to do the same.
Here is my demo form: https://form.jotform.com/70195009299967
Feel free to test it and clone it.
Hope this will help. Let us know if you need further assistance.