When I upgraded to Yosemite, I happily used Notification Center to receive alerts upon getting a message or so. I then turned them off at some point and recently changed my password (not sure if that matters). Since then, despite the notification type being set to "Alerts" and having updated the password in
Internet Accounts, I do not receive Notifications. I can use the notification center to post to Facebook, which makes it weirder.
The problem does not appear to be exclusive to me (see these discussions). I tried removing and readding the account, turning off Little Snitch, resetting SMC (can't imagine why that would help, but it fixed it for some people), but no. Does anyone have any suggestions what to do?