Subractive Brush Type not subtracting

I am trying to use the ‘subtract’ brush type function with a standard Box on the wall of the 3rd person Example game that comes with Unreal. I have it setup in Mobile mode.
For some reason the box does not cut the expected hole into the wall. The box I am trying to cut with just changes translucent, showing the wireframe. And if I change it back to ‘Additive’ it changes solid with the checker pattern standard grey texture.
I am looking at the scene in Lit View mode.
I have done this before starting with the basic tutorial and never had a problem.