It just doesn't paint anything. I have a prefab selected in the brush in the Tile Palette, and it is in edit mode and I click and nothing draws. I created a GitHub issue request at https://github.com/Unity-Technologies/2d-extras/issues/177. Muchos gracias, mike
Just to check, are you trying to use the Prefab brush on the Tile Palette? That is currently not supported yet for Unity 2019.2, and you can only use it on Grid/Tilemaps in the SceneView.