Form Will Not Redirect After Applying Coupon Code


I made a form with HTML which applies a coupon code. This form (with a textfield to fill in the coupon code and a button to submit) is placed on a page created in CS Cart.

I want the page go to the homepage after applying the coupon code, but instead, when hitting the submit button, the user stays on the same page and doesn't redirect, even though I have used the hidden redirect_url value.

The code is as following:

Can anyone tell me what I'm doing wrong?

Thanks in advance,