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I have tested your form on my Samsung Galaxy S4 and on my android tablet and I was able to submit your form.
Also I have inspected your form on your website and I noticed that you are using script code for embedding your form on website. We recommend using of iFrame code. You can try to replace script code with iFrame to see if that will resolve your problem. In this article you can find out how to do it.
Hope this will help. Let us know if you need further assistance.