When I've had this problem, I realized that the areas/elements I had created had gotten moved off the edges of the actual mural canvas. I extended the size of my mural board so that the elements I wanted to show were inside the boundaries of teh mural board and all was fixed.? That's hard to see if you have colored your mural board with a full size image or other colored element, so you'd have to move that out of the way to get to the very bottom mural board layer to see if the elements you want to show are inside or outside that boundary.
Linda
Linda Howard