Well I didn't want to influence you too much at first, after a few attempts I isolated the source of the problem.
My surface piece is a derivative part (to share sketches)
I make it a volume with the sew function then I click on the Form Tool function, there 1st bug, error message "no volume detected" except there is indeed a volume in my design tree.
I make a derivative part of my derivative part, this time the shape tool works, successful parameterization but when the time comes to use it problem, I drag on my sheet metal nothing happens.
So I create an assembly with my derivative part and then I save in part format (sldprt)
In this new piece I just have my shape in surface, I sew it in volume, I use form tool, I record.
I go back to my sheet metal, I slide my stamped form and there it works.
Conclusion: a derivative part cannot be used as a tool of 0_o shape.