I am "stuck" on the desktop. Clicking the dashboard icon does nothing, I cannot use the 4-finger swipe gestures to move to or view the dashboard or any application windows in fullscreen (yes, I have checked system preferences, it's on), and the function key that usually allows me to see fullscreen windows+the dashboard+other desktops does nothing. I have tried shutting my computer, quitting everything and restarting. If I open another fullscreen window, I am stuck there until I close or un-maximize it. This has happened before and it went away after a minute or two, but it's sticking around now. I have a MacBook Air running on Mac OS El Capitan.
How can I solve/prevent this problem?
UPDATE: It has started working again, but was stuck for much longer this time.
This problem is continuing off and on.