Can't open my notification bar while using any other app

[Android Central Question]

I am using vaga A900 Korea Mobile and it was working completely fine but now i have one issue.
when i am on a home page i have access to notification bar but when i am using some app e.g. whatsapp or facebook or any other app i can't drop down my notification bar.
anyone please help me out

 

[B. Diddy]

Welcome to Android Central! Does this happen in all apps, or only certain ones? Do you have a screen protector on?