Skylight is not affecting the scene not working at all

Hi I am new to UE just started learning it. Some issues I have ran into.
I have started the scene in Architectural category with a blank template which has SunSky ExponentialHeight Fog.
I have deleted all the lights. Added a directional light and a skylight. Want to use Skylight as ambient light. But somehow skylight is not affecting the scene, only dir light is working and when dir light is turned off everything is black. Dont want to use cubemap source type in skylight. Tried all mobility option, as well as affect world in skylight and even when the intensity to 50 to 100 nothing working.
Am i missing any important setting?
Any help much appreciated. Thanks