Can't render ray traced shadows

I have a simple test scene, a Cornell box with the color calibrator and a single Spotlight.
I am set up for hybrid lighting, ie baked GI and Ray Traced Reflections and shadows,

Ray Tracing is enabled and my Spotlight has ‘Cast Ray Tracing Shadows’ enabled.
The color calibrator has both ‘Cast Shadow’ and ‘Dynamic Shadow’ enabled and its Mobility is set to Movable.

Why isn’t the color calibrator casting ray traced shadows?

is raytracing enabled? dx12 and all that?

yes. I think the issue is Cast Raytraced Shadows must be disabled on the source to cast shadows.
Counter intuitive.