I assume you mean after submitting the HTML form the confirmation is not being shown, and not in the Options tab editing the form when signed in. What happens when the form is submitted in IE11?
My forms work fine in IE11 displaying the confirmation message/page.
Can you email me the link to your form to test on IE11 to see if I see the issue? email@example.com
Can you also confirm you are using the HTML/Web form and not a PDF?