Why does it return html when there should be a redirect?

Question

Web servers

I'm trying to make a request for one online store. I send data. I tracked all requests in advance through the Http-toolkit program, and according to the idea, after the last request (which I make) I should be redirected to the page "Your order has been successfully created" but this does not happen, I only receive the markup of the data filling page. What am I doing wrong? Please, help