Yes, I'm using the traditional web.
I looked at your oml but couldn't get a solution.
Are you trying to open the file in the same version of MSOffice it was created on?
I got it to work using an xlsm file created in my Excel and downloading it with the Mime-Type "application/vnd.ms-excel.sheet.macroEnabled.12", maybe it has something to do with the difference between MSOffice versions.