Terrain details do not render in a build but they render fine inside the editor.
Make sure that there is a game object in your scene with a Global Wind component. Without it, terrain details do not render if they are using any of the Open World Nature shaders that come with Nature Renderer.
The shaders don't render because they require some global shader properties to be set, such as the wind strength and wind direction. If they are not set, they default to a value of 0 which causes some calculations in the shader to result in a NaN result. These global shader properties are set by the Global Wind component.
We realize that this can be inconvenient and are working on a fix to apply default wind settings in a build if there are no wind settings in the scene.