Error : The WebReady Document Viewing service has been disabled by the administrator for your organization. For more information, contact your helpdesk.

I followed this topic 'http://technet.microsoft.com/en-us/library/jj150495.aspx' to integrate office web apps Integration with exchange 2013. But i got below error after clicked document preview in OWA. I have enabled public and private attribute to ture.

The WebReady Document Viewing service has been
disabled by the administrator for your organization. For more information,
contact your helpdesk.

Clarence Mei