SharePoint 2013 Office web app server error.sorry we couldnt open this presentation because we ran into a problem. please try again

Hello Everyone,

I have configure OWA for SharePoint 2013. when I try to open any document (PPT, DOC, PDF) I am getting different error.

when I try to open PPT I am getting below error. 

PPF:- "sorry we couldnt open this presentation because we ran into a problem. please try again"

Word:- Sorry there was a problem and we cant open this document. if this happens again, try to opening this document in word.

Please help me here. please