Each time I add a new light into my blender scene it doesn't show up or have any effect on the environment. I tried increasing the strength and messing with the translate, rotate, and scale of the light as well as trying different kinds of lights. But no matter what I do it doesn't show up or have any effect on the render.
I had the same issue and it was because i was in the local view (Numpad /), didn't realize it before i figured out there were no layer selection.
hope this helps someone to not be stupid like me.