Hi Samuel,
I haven’t watched this course yet, so I don’t really know what’s going on, but from what I can see in your screenshot, I’d say that it is working, but the size of the dirt is very large. Your using Object Coordinates and a Scale of 3 for the Noise Texture that controls the dirt. And your Object is very small, so you only get a tiny part of that Noise and in your case that is mostly dark.
