During the checklist the rendering of the 3D view is "empty" when selecting the "CT Bone (with gradient)" option.
But this is not a technical issue but a logical.
The settings inside the Grayvalue/Gradient->Opacity are set in such a way, that nothing will be displayed and for sure - that's correct!
So maybe this should be noticed in the checklist Test4 actions, or maybe a different image should be used, or the settings should be different ... :-D