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None of mine work either, I figure I'll give it a few days. Then I'll do a reboot and see what's up.
 
Not having this problem. Mail, Twitter, Messages, and Calendar notifications pop up right away.

Try a reboot or just try turning them off and then turning them on again.
 
Mine actually started working this morning. Didn't do anything, just fixed itself I guess.
 
I did a restart and still no notifications.

I'll probably try these steps next:

If its a MBP with a battery you should not remove (like mine),
SMC reset:

Shutdown your machine. Plug in the adapter.
Hold Shift+Control+Option+Power button at the same time.
Then release them at once say after 3 seconds. (it should not start when you press the 4 keys for the SMC reset)

Then hit the Power button to start.

Once started and you hear the beep, hit Command+Option+P+R immediately for the pram reset.

Keep holding it till you hear the start beep for the second time. (it would be an internal second restart)

Then release it for the restart to continue.​
 
are they set up properly in mail, contacts and calendars under system preferences? Can you connect to them through the mail app, but they don't show up in the notification center?

try sending yourself and email to get the ball rolling. Perhaps it does not kick in until a new message is received (ie, after the account is set up, so older messages do not appear).
 
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