How do I enable HSL Vibrancy in Photolab 7.0

My HSL Vibrancy slider is currently disabled. Can somebody please let me know how to enable it?

Thanks for all your help.

The Vibrance is only available when the white (all colors) channel is selected. Luminance and uniformity are not available.

When a color channel or eyedropper is selected the vibrance drops with luminance and uniformity available instead.

In order for Vibrancy to appear ungrayed, then no specific color( the white channel) must be chosen. In your situation, click the reset button, then click the white channel button and your HSL palette should look like this.