I had an issue with Sapling Generator. Under the Properties -> Render Layers tab. If you try to add a sapling to a Scene layer which isn’t highlighted, it will just create the sapling on the next available highlighted layer.
Even if you are viewing that layer in the 3D View, it still won’t place the sapling there.
I dunno why it’s like this, because you can create meshes without the layer being highlighted in the Scene layers, but the sapling addon didn’t like it.
Also, in blender v2.78, the addons setup is different then the one in the course.