This question already has an answer here:
Up until today, when I would get a message notification from Facebook, it would say the content of the message and the sender. I had to delete and re-add Facebook to my "Internet Accounts" preference pane because I changed my password. Now it just says that I have a "New Message" whenever I get a message. How do I change it back? Re-adding my Facebook account and restarting don't fix it.