Can you give us some more details on exactly what's happening?
What version of JMP are you using? What are you trying to drag and drop? Which part of the drag and drop operation is failing, the drag (i.e., you can't pick up what you want) or the drop (i.e., it won't go where you want it)?
Do you get an error message? Is this happening with all Graph Builder platforms or only after you've built a specific graph?