How do I add displacement to a mesh?

I feel like the answer is simple by I'm stuck and hoping someone can help.

For context, I'm trying to add displacement to a simple block so I can export the mesh with that displacement.

The sample project "tiling material" showcases what I'm trying to do but when I create my own project, duplicate the layer stack, and make sure the display/shader settings are identical, I'm coming up short. The mesh just will not displace when I adjust the height parameter. It seems to only move the entire face.