OSX Yosemite - Mission Control stopped working

Not sure how long this has been happening, but I just noticed it AFTER Yosemite update.

Mission control just does not work: using hot corners, keyboard shortcut, or even double clicking Mission Control.app, there is no way to make my Mac go to Mission Control/Exposé. By the way, I have hot corners for showing desktop and app windows exposé, neither of which work. Hot corners for dashboard and Notification center work as usual.

Any ideas why does it happen, how could I solve it?

Thanks a lot.

Solution 1:

(This irritating bug seems to be biting me more often after updating to 10.10.4)

When this happens and I don't want to have to reboot, I only restart the "Dock" process and the problem is gone. There's probably some GUI way to do it, but I just drop into Terminal and do:

killall Dock

But before that, run killall -s Dock to see what would be killed, to make sure it's only going to directly kill the one "Dock" process.

Once you run killall Dock, Dock will restart in a few seconds and then Mission Control is working again. You can verify that the restart happened by checking the Process ID of "Dock" after the restart.

Solution 2:

The GUI way:

1. Open Activity Monitor.
2. In the search field, type in 'Dock'.
3. Select Dock in the results.
4. Click on the black X directly above on the left.
5. When asked if you are sure you want to quit the process, choose Quit.

The Dock process will quit and restart. All your gestures/shortcuts will now work again.

Solution 3:

I found that the file responsible ist com.apple.dock.plist which sits in ~/Library/Preferences. In this file exists an entry to enable/disable mission control.

For me this procedure helped to get mission control working again:

• Start terminal and execute the following commands:

• defaults write com.apple.dock mcx-expose-disabled -bool FALSE
  (this enables mission control)

• killall Dock
  (kill and automatically restart the Dock, this is necessary to get it done)

Solution 4:

I had this issue as well when I updated to OS X El Capitan (Version 10.11.4). Found out my dashboard got switched to "Off." What worked for me is to:

1. go to System preferences
2. open Mission control
3. make sure "Dashboard:" dropdown is set to "As Overlay".

Solution 5:

I just had a similar problem (also under Yosemite) - mission control was still accessible with function keys but not with gestures. It came back with a reboot.