404 error is appearing after submitting the contact form?

This is mainly because of the element names “name”, “product”, “day”, “month” and “year” in the contact form.

WordPress won’t allow to use  these names as element name.

So please go to the “Edit element” section of the contact form manager/XYZ WP Contact Form and rename the elements “name”, ”product”, ”day”, “month” and “year”.