I created material to use for a landscape. When applying the material to the landscape the 3 different textures I put into the material showed up and applied to the landscape correctly. The problem is that it is very dark. I noticed that when I created a new material the background behind the sphere is also dark.
set the metallic and specular to 0 in the material. and rebuild the lighting, if your lighting is still too dark you can increase it in the directional light / skylight. if the light is pointing the wrong way you can rotate the directional light.