This error is not unusual when configuring excel services and trying to display an excel document inside the browser. OK, so what to do then?
- First step would be to check the SharePoint log and the event log for errors
- Check that the account running the excel service application has “db_owner” rights to the SharePoint content database. (http://blogs.msdn.com/b/jjameson/archive/2010/05/04/the-workbook-cannot-be-opened-error-with-sharepoint-server-2010-and-tfs-2010.aspx)
- If you get this error in the event log “The data culture ‘X’ was requested, and it is not fully supported because its language pack is not installed. Some features will not be available.”, install the language pack for that specific country and run the configuration wizard. (http://www.kowalski.ms/2008/07/04/excel-services-was-unable-to-load-the-workbook-that-you-requested/)
- See an “System.InvalidOperationException: Could not retrieve a valid Windows identity.” error in the ULS log? Make sure “Claims to Windows Token Service is started in Windows Services
- Also, check if Claims to Windows Token Service is started in central administration (Services on server)