NormalMap on SurfaceAppearance darkens transparent area

The main issue I am having is that when I apply a NormalMap to this texture it turns dark,

The NormalMap is a PNG and all the transparent areas are… transparent

Removing the NormalMap removes this darkening effect:

I noticed this issue when I was messing around with my lighting settings and decided to turn it to all dark as I noticed in more typical lighting conditions it was darkening the material below it.

Help would be much appreciated

Just realised that even w/o the NormalMap the middle does not change depending on material selected

Only the colour selected can be seen, if anyone knows why this is please help.

EDIT: Using the devforum post below I am able to get the middle to be transparent when not using SurfaceAppearance, but I really want to be able to use a NormalMap which requires SurfaceAppearance to be used.