Facebook messages don't appear on Iphone4s lock screen anymore?

I've had my iPhone since November and when someone inbox's me on Facebook its always came up as a banner on my lock screen but all day today its not been working even though someone inbox-ed me. It didn't come up as a banner. I had to go onto Facebook app to see what they put.

I've checked the settings and everything's on and how it should be, I don't understand what's happened. I've turned my phone on and off a million times but nothing is working!

Can anyone help with this please! Is so annoying!

Https://www.facebook.com/help/