You may have noticed that the thank you page does not appear after your recipients submit their subscription requests through an embedded sign up form. Instead they'll see a "Success" message. This is something that we're working on and we hope to add a Thank You page soon. In the meantime, you can choose the "Share A Link" option and share the URL with your subscribers. If you understand HTML, you can use an iframe within the HTML code on your website pointing to the URL for your sign up form. This will give the appearance that the form is hosted on your website and go to the Thank You page as you intended.