Lighting Shadows On Landscape Are Plain Black

I'm encountering a frustrating issue with my landscape: all the shadows it receives appear completely black, while other meshes, objects, and foliage in my scene receive normal shadows.

Has anyone experienced a similar issue before or knows what might be causing this? Any insights or suggestions on how to troubleshoot and fix this problem would be greatly appreciated.

Shadow on Landscape:


Shadow on mesh:

 

edit: fixed it by setting ambient occlusion to 1 if there is no texture for this specific layer