Office Web Apps Previews Not Working in SharePoint 2013?

Excel and PowerPoint Web Apps also failed. "Excel Web App - Sorry, we're having a problem showing this workbook"

Analyzed event logs of SharePoint and OWA servers and found nothing useful. Logged in to the Office Web Apps server and Analysed the latest log file from "C:\ProgramData\Microsoft\OfficeWebApps\Data\Logs\ULS" location.

While scanning LOG files, found these lines:  "WOPICheckFile,WACSERVER FileNotFound [url:http://sharepoint.crescent.com/_vti_bin/wopi.ashx/files/7529f29d45234898b81a46a14a74203b?access_token=REDACTED_1072&access_token_ttl=1418077932722"

Well, Office web apps server must be able to resolve and communicate with SharePoint 2013 sites to render office documents in SharePoint sites. In my case, It couldn't do that because of a WRONG IP placed in the HOST file of Office Web Apps server! I just fixed it by clearing HOST file entries and creating global DNS record for SharePoint sites! You can also try placing a HOST file entry in Office web Apps server, pointing to SharePoint sites, if DNS change isn't possible.