When I first upgraded to OS X Yosemite I was able to receive Facebook Notifications (such as new private messages) on my OS X Yosemite Notification Center with a pop up window. I did so by correctly configuring my Facebook account information on System Preferences. A few weeks back I noticed that I was no longer receiving such notifications even tho I was still able to post to Facebook through Notification Center, confirming that my account was configured correctly in System Preferences. Does anybody know how can I fix this issue? or maybe tell me if this is a recurring error/issue with OS X Yosemite at the moment? Thanks in advance.