Cannot Paint Landscape Layers

I followed this tutorial

It was very helpful, at first I had my entire landscape black but was able to fix this by right clicking a landscape layer and clicking Fill Layer. Now I am trying to paint other layers on top of my grass. When I select the layer and attempt to paint Dirt on my landscape nothing happens, it just keeps the grass....

I’ve looked and found a few similar questions online but nothing that has seemed to help. Was wondering if someone could walk me through what I’m doing wrong. Here’ are two screenshots of my layers and the material blue print.

https://imgur.com/a/wrbhR0r