Lighting feature is disabled as default. You'll have to enable it in options.
OPTIONS > GRAPHICS > Map Shadows & Lighting Selections

There is a command to optimize performance of lighting engine in real-time.
shadow_frameskipping <UPDATE>
This command allows you to avoid unnecessary lighting updates.
Though, the effect might be seen while using flashlights or other real-time features.

<UPDATE> Parameter
1 - every frame (very slow)
2 - every second frame (slow-default)
3 - every third frame (fast)
4 - every fourth frame (very fast)

You can also find this feature in options.
OPTIONS>MORE>ADVANCED GRAPHICS

There might be several problems in this case.
Shadows engine is disabled.
Flashlight works only in "Env_Room" areas.

As some people may have noticed, there are "shadow_shadewall", "shadow_shadeobstacle" commands.
Shading adds smooth black edges around the objects.
Here you can see the effect.
In Left: Wall shade = 1; Obstacle = 2.
In Right: Shading is disabled.

Lighting feature is disable as default.
In order to see the shadows in map editor you'll have to enable it first.

To use lighting effects in your map you'l have to meet the requirements.
The Largest Map Size: 100*100 (X*Y)

To see the lights, it's necessary to create a room first.
So take an "Env_Room" entity and drag it on the place you want to have lighting effects.
Remember that huge rooms with "Shadow Height" parameter on may lead to several issues and crash the game.

So now we have a room and it's put the lights there.
We can also customize it: Set a different color or enable dark wall edges.

As an example I took ctf_fast map and created a huge room over the map.
To create a light source, you'll have to select Env_Light.
Create a light source is very similar to BombSpot: after setting the light position you must drag mouse and choose the radius you want.

There are some additional features in this entity.
ANGLE: Alpha & Beta that will changes the light ray's direction.
ROTATION SPEED: Useful when using different ALPHA & BETA angles.

We are going to use "Env_Strips" as smooth transition from Day Lighting to Room Lighting.

Probably Gonna Be Some

Probably Gonna Be Some