When I receive any notifications in Sierra, they display on the screen as banners, then show up in the Notification Center and automatically disappear after two minutes without any interaction. Example: Notification banner is displayed on desktop without any interaction by me, it eventually disappear as you would expect. If I then open the Notification Center, the alert is displayed and will dissapear after two minutes right before my eyes without any interaction by me. So basically, if I don't happen to catch an alert in then Notification Center within two minutes of it being received, I will miss it permanently. This is happening for ALL of my alerts. This certainly can't be by design as it would make absolutely no sense to even have a notification Center. Any ideas?