Your camera is 15km up in the sky. You can barely see the terrain in detail at that altitude, let alone strata.
Consequence of that is that you set the blendshader altitude constraints to 13000m and higher as well.
I think you have moved your camera somewhere into the canyon but forgot to "confirm" the new camera position by clicking on the bottom left of the preview-render (it has a small camera icon with an arrow below it pointing to the right....click on that button and the current camera position will be updated).
