Hi Silva! Depending on the ability that you are dragging, there may be nowhere for it to go. The NPC sheet does not have the same attributes as a PC sheet. There is nothing like a "class feature" for instance, since NPCs don't have classes. If you were to switch it to the PC sheet, you might some of those features appear (i.e. it is still accepting the drop, but the NPC sheet has no places for a class ability to display). Your best option in such a case is to create a new action or feature on the NPC sheet and copy and paste.
