How do I re-enable Notification Center in Yosemite or El Capitan post-upgrade? I believe I followed the advice here: How do I permanently disable Notification Center in Mavericks?

Post upgrade to Yosemite, the Notification Center icon shows up in the menu bar, but clicking on it does nothing, as noted by this individual: https://apple.stackexchange.com/a/142921/96853
This in Terminal will show Notification Center again:

launchctl load -w /System/Library/LaunchAgents/com.apple.notificationcenterui.plist
killall NotificationCenter


You will have to restart your Mac afterwards.

Reported to work in El Capitan (10.11.1) as well.