Hi,
first of all: I am a total UE4 beginner! I followed a few tutorials from the UE page and I was about to experiment with the material editor. But I can’t really see anything in the Material Editor Viewport. (picture example) I checked all the viewport settings, it is on “lit”. I know, it is a noob problem and I am probably one click away from the solution, but I can’t find it! Thanks in advance for any help! 
Did you accidentally move the light source? Hold L and drag the mouse around in the viewport.
Thanks for the quick answer, but that didn’t solve the problem. If I click “L” a white arrow appears, which indicates the light direction, but it has no impact on the scene
is it the same with all the other materials?
Yes, no idea, somehow you’ve got a sunset there… :-/
also, do you have auto exposure enabled? (tick lit => auto exposure)
Yes, it is with all the materials
I’ve got it. You accidentally tweaked the preview scene settings:
if you don’t see the preview tab, use window → preview scene settings.
Just put everything back to default. I suspect you tweaked the skylight, it should be 1.
Yes, you’ve got it! That was the problem!
It seems I messed up twice: First I unintentionally tweaked the skylight setting and I somehow managed to close the "Preview Tab in addition, so I even didn’t gave myself the chance to figure it out on my own.
I really appreciate your help! Thanks to everybody how tried to solve that problem!
Noob out.
