Why is there a black bar going down the side of my tilemap?

This black bar on the right side won't go away. Any idea what might cause this black bar to appear in my tilemap?

I am seriously thinking about going back to Unity. It seems like everyday something like this comes up. This program was supposed to be easy to use, it's become a nightmare!

What black bar? You mean this?

Most likely the image in the tilemap is slightly misplaced. Try double-clicking this tile in the Tilemap Bar to check.