The first time you open the sheet, Excel will open in protected view, which is intended to stop harmful content from accessing your computer. This is entirely normal and will happen for any downloaded spreadsheet, Click “Enable Editing” to continue (This warning will not show again.)
Excel will also show a “Security warning” for the use of macros and by default disables them. This warning will show every time the sheet is opened. The only way to disable this is to disable the warning (which is not recomened) globally. Click “Enable Content”, and ExclCSO should be fully functioning.