Range Skeletons should be placed on the gridded places side, not on the path where the enemies come from. There are 2 different textures indicating this. You can try again if there is another error we can take note :D
I tried it again and I see what the issue for me was. It says Left Click will cancel trying to place a Ranged Unit, and Right Click places the ranged Unit.
It was the opposite for me, which is what would seem intuitive. As in, place the unit with Left Click.
