For several weeks, I haven't been able to go full-screen in any app on my laptop. I thought it was a Chrome problem with YouTube, because when I hit the full-screen button in a movie (bottom-right corner of the movie) it will expand to fill the browser window, but not the whole screen. Then to restore, hitting Escape or the exit-full-screen button doesn't get the video to reduce down again. Reloading the browser page works, though.
However, it's not just a browser problem – I recently discovered that no apps (e.g. Finder, Photos, Terminal, Console) can go full-screen by clicking on the circular green button on the left side of their window bars.
On a random cargo-cult recommendation I saw here, I trashed my ~/Library/Preferences/com.apple.finder.plist file & restarted the Finder, but no differences are observed.
When I hit the green maximize button in a Finder window, it seems to crash that window – I can no longer drag that window around & it doesn't respond to any clicks. Other Finder windows stay fine.
To try to debug, I've poked around in various system logs, but I haven't found anything that looks relevant. Maybe something to do with the WindowServer?
I'm on a MacBook Pro (Retina, 15-inch, Mid 2014), running Sierra 10.12.5.
Best Answer
Tried a couple more things, and here's what worked: kill the Dock, then get it to restart. I did this by doing
killall Dockin the Terminal. It didn't restart by itself, so e.g. Cmd-Tab didn't work to switch applications, my desktop had no background, and (of course) there was no Dock.I launched the Dock again by going into System Preferences & clicking on the Dock pane.
Why did I try killing the Dock? Because I also noticed that Exposé/Mission Control wasn't working either. Some searching led me to this question, which suggested restarting the Dock.