PPTX not getting edited

We are using office 365 in our application for editing docx, pptx  etc. on office online.  We have office 365 setup done on our server. When we edit docx, it works fine. But when ever we try to edit pptx, it gives error. You can check error in file attached here in. When we checked out console it was showing error in "ppt/view.svc/jsonAnonymous/GetFullSizePreview" function.

Thanks