Why has my action center stopped working on Windows phone 8.1 update?

[Windows Central Question]

I have Nokia lumina 625 that has been great. All of a sudden, and I think it was after an update, the action center has stopped working. When I swipe down the screen still moves but the action center does not appear. Any ideas as this is very annoying as I used it a lot, also lost the notification part of screen as well. Have I turned something off by mistake?