In macOS Activity Monitor, why is "Applications in last 12 hours" grayed out / disabled? Any idea why the "Applications in last 12 hours" is disabled in the "Activity Monitor"?

At one point it appeared briefly -- but after days of using it, it has since disappeared. 

Using macOS 10.15.2. Many thanks.
It's only available on the Energy tab.



I can just tell from your pic, you're on the Disk tab.