Exponential Height Fog is not working

Exponential Height Fog has no effect on the level. Adjusting the fog density has no effect either.

Tested in 4.11 stream CL-2811790

1. Open UE4
2. Use any map, New Default Map works well enough
3. Add an Exponential Height Fog
4. Adjust the Fog Density to a higher value

Results: No effect when using Exponential Height Fog

Expected: Exponential Height Fog should have some impact on the level with higher fog density

Regression: Yes