Noob question - my landscape doesn't seem to work properly with directional light

I am not sure if this is a correct question to ask questions like these, so I apologize in advance if it’s not. I couldn’t find any section specifically for questions like these.
I’ve combed the internet but to no avail.

When I create a landscape in UE4 with my custom material, the directional light (which I use as the sun) only lights it up when directed from below. This is in reverse to meshes, which behave normally as expected.

My material for Landscape is fairly basic with 3 layers. Nothing fancy in the blueprint.

Check your normal map, probably inverted green channel