Why am I not able to take screen shot on my Lumia 640?

[WPCentral Question]

i dont know whats gng on in my mobile.. finally when i tried to take screen shot with my lumia 640 iam no more able to take screen shot with my lumia 640 insted of that it saying that couldn't take screen shot... why this happening... some one please help me

 

[Guytronic]

Which button presses are you trying to get the screenshot with?

 

[jinu sabu]

Use lock and volume increase button..

 

[Fatima nabil]

I have the same problem what can I do to solve the problem?