This has happened to me a few times since upgrading to macOS Catalina (10.15.1) and the root cause is unclear.
I am downloading something using Firefox, in push Firefox away to do something else, I go to use Safari — or a text editor — and then… Like magic… The screen goes dark… Not sleep… Just dark… And I can’t see the desktop or anything.
I know the underlying system is still up and running because if I SSH into it from another device/system I can see the OS is still alive and not hung. And in the case of the download, I can still see data being downloaded using the command line tool
nload (which I installed via Homebrew). And past that the brightness controls on the keyboard still work… But obviously the screen is dark — and not turned off because of sleep mode — and I can’t see anything.
Now, under most circumstances, I would just say a few “choice” words, hold down the power button and wait for the machine to come back up via reboot. But this download is in progress so I don’t want to do that.
So what can I do to get the screen on my MacBook Air active and viewable again?