The action button shadow is not rendered. This is due to the following line in the RectangularGlow component of FloatingActionButton.qml:
visible: control.enabled && control.Material.buttonColor.a > 0
Material.buttonColor is apparently a function, so buttonColor.a is undefined and the item is never visible.
How it looked with FluidMaterial.ActionButton at 60ff2cf:

How the FloatingActionButton looks now:

The action button shadow is not rendered. This is due to the following line in the
RectangularGlowcomponent ofFloatingActionButton.qml:Material.buttonColoris apparently a function, sobuttonColor.ais undefined and the item is never visible.How it looked with

FluidMaterial.ActionButtonat 60ff2cf:How the
FloatingActionButtonlooks now: