Pro Form - New Post Featured Image not added to Post

Please Help
I have a Pro Form that creates a New Post with - Title, Content, Featured Image.
Everything works except the Post Featured Image.

I am able to see the thumbnail when filling out the form. And The image is added to the media library.
But it isn’t connecting to the Post Featured Image.

That would leave me to believe the field ID is wrong, but it is correct.
my_featured_image is the Custom ID. {{my_featured_image}} on the form action

Is there anything else I am missing?