Ok I see your problem.
Your GameObjectTiles.bmp doesn’t have the correct dimensions.
So what you need to do is: use the selection tool, select all this graphics. Copy it (CTRL+C).
Make go to the menu « pixel editor > new > Game object tileset », move your mouse cursor to the top left corner of the tileset and paste (CTRL + V).
Then save the file in your folder with the name GameObjectTiles.bmp, replacing the existing one.