Hi. I keep getting this error when I submit my form:
Warning Message body empty. However, the form get stored under Submissions in the backend, but it doesn't send the email to the user or the admin.

Hello,

This points to the fact that you have an empty body on your message. While editing the form > Properties > User/Admin Emails > edit the email body and add some contents. Simply configure your form's emails normally using your form's placeholders, you can view your form's specific placeholders by clicking the Toggle Quick Add button (located in the upper-right corner while editing your form's emails).

However note that within a multi-language website, notice while editing a form in the top left corner, a language selector. Make sure that you edit the form emails using the same language that you're testing this in the frontend area.

Hi. I followed your instructions. I am now getting this message when I submit the form on the frontend: Warning Could not instantiate mail function. And I also et a Mail Failure email.

Please take a look at this article.