Windows 10 Display Won’t Sleep/Turn Off (Tried Everything!)

No mention if this is a laptop or not. I’m going to assume it is due to the “battery/DC” comment you made about Power & sleep settings.

What I do is none of that. I just set the power button to turn off the display when pressed and then manually turn it off when I walk away:

  1. Open Control Panel
  2. Power Options
  3. On the left panel: “Choose what the power buttons do”
  4. “When I press the power button:” -> “Turn off the display”

This isn’t fool-proof; if someone hits a key or knocks the mouse (heck, even if the table vibrates by someone walking past it!) the display will wake back up.

All that said, unless you absolutely need the computer to stay on 24/7, just turn it off when you aren’t using it.

…and if it does need to stay on 24/7, why is a laptop being used in the first place?

For a desktop the situation is the same: Just turn the monitor off.