Notification center won't open

I have a MacBook Pro and recently my notifications stopped appearing on the right-hand side of my screen. The main apps I have notifications turned on for are my email and iMessage. The notification sound still plays when I get a message and the little number on the app appears, but the actual preview of the notification doesn't show up. Also, when I click the notification center icon in the upper right-hand corner of my screen, nothing happens. I've already gone to system preferences-->notifications and made sure that my app notifications are turned on. I've restarted my laptop and that didn't help either. Any ideas on what else I can do?