Solution
If [ : Highlight tone priority] is set to [Enable] on your camera, [Auto Lighting Optimizer] is automatically canceled.
If you wish to enable [Auto Lighting Optimizer], set [ : Highlight tone priority] to [Disable] first, and then set [ : Auto Lighting Optimizer] to [Enable].
For details on how to change the shooting menu settings and how to set [Auto Lighting Optimizer], please see the instruction manual supplied with the camera.