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According to my checks on your page, it seems that you have already embedded your form with iFrame embed code; but as it is seen from the below, you don't need to take the whole structure of embed code, the content between <iframe>...</iframe> tags is enough to embed your form. (Following code is just an example, don't embed that one.)
Also, you can check the following guide to make sure that you have followed the correct steps while embedding your form.
I hope this will work for you. Please, try this one and let us know the results.