Constant Contact / Formstack Will Not Display in Slide In

I want to display my opt-in form in the slide in. However, when I try, the slide in is just empty.

this is the code they say to paste in:
<noscript>Online Form - Constant Contact Signup Form</noscript>
<div style="text-align: right; font-size: x-small;">Web Form Generator</div>

It works on the site, but not in the slide in.