Eyedropper Tool - trying to sample all layers, but the control bar isn't showing that option

Hi all, I am trying to make my eyedropper tool sample all layers. Supposedly I should click on the eyedropper tool, then the control bar will show the option to select 'sample all layers'. However, when I click on the eyedropper tool, the control bar doesn't change (not showing any options for eyedropper tool settings).

Any help on this would be greatly appreciated. Thank You.