Windows 8 notification popups?

[Jibran]

I am using windows 8.1, and i have the downloaded facebook app from the windows store. Sometimes when i change tabs for example i go from facebook to google chrome, etc i expect to see a notification pop up on the top right corner when i receive a message, however it only comes sometimes, can i know the reason why? And how do i make it appear every time i receive a message. Thank You!

[FemaleLotRfan]

It's probably just an issue with the app