I'm trying to get a form displayed when we click a "preview" button on EC. I have a custom object and the form is based on this object. I've created the modal dialog and entered the correct group code for displaying the form. When I test it by clicking on the preview button, I see the modal dialog which says "Generating PDF" but gets stuck there. I've followed exact steps from 18.104.22.168 Create a Preview Button for a Print Form as per SDK doc.
Can someone please let me know what I'm missing.