When attempting to use Office Web Apps with SharePoint 2013, some documents may display this error message:
“Sorry, we’re having a problem showing this workbook.”
Some documents are unable to be shown in Office Web Apps (both in the browser and the preview screens). This is due to the fact that some documents may contain sheet protection, macros, and other advanced functionality which cannot be loaded into the browser. This behavior is “as-designed” and users should be instructed to open those documents in the Excel client.