You need to check the box "Show Grid While Cropping" in the crop pane. See attached screenshot.
And in addition, the new Grid tool offers an option to Show the grid, or not (to avoid clutter), and whether to follow the crop contours, or the original image contours (see attachment). That provides lots of customizable control over the tool, including a choice of grid-color, or other settings that are relevant to only a specific type of grid.
It is a kind of a default setting that applies to all images, but one can easily switch settings should e.g. a different color be better for one specific image.
Cheers,
Bart