Mavericks: notifications no longer displaying
First, check your settings in System Preferences > Notifications. You may have Do Not Disturb enabled.
  
  For com.apple.notificationcenterui.plist. It's located in your user library, not root level where you may be looking.
  
  Open the Finder. From the Finder menu bar click Go > Go to Folder
  
  Type or copy paste the following:
  
  ~/Library/Preferences/com.apple.notificationcenterui.plist
  
  Click Go then move the com.apple.notificationcenterui.plist file to the Trash.
  
  Restart your Mac.
  
  I can't locate the com.apple.soagent.plist in either user or root.
  
  If deleting the com.apple.notificationui.plist file did not help, reinstall OS X >  OS X Mavericks: Reinstall OS X
  
  That will reinstall any missing system files required for the Notification center.


From https://discussions.apple.com/message/25351691#25351691