I created the tool with 2019.3 but it may work in earlier versions as well. Have you added the material to the materials list that you are showing in the picture? How does the material look? It's provably best if you could record a quick video.
I will download 2018.4 tomorrow to see if that has an effect on anything but I'm guessing that you are creating a new project so what is holding you back to that Unity version?