Note: This question is essentially a duplicate of Windows 10 “Night Light” and “Brightness” options not active and Night Light disabled in Action Center, but the first has no answer and the 2nd has an answer that did not solve the problem.
The night light option is greyed out in the Notifications panel, the Display settings, and Night light settings. Additionally, a search for "brightness" in Settings yields no results!
Things I've tried: 1) Changing the time zone 2) Restarting the machine (an HP laptop) 3) Checking for Windows 10 updates even though I just updated 4) Online searches, and 5) Microsoft's Virtual Assistant