Microsoft used to have an Excel Viewer but it is retired, though it may still work.
Download the latest online Excel Viewer - Office | Microsoft Docs

If you don't have an MS Office license I'd suggest LibreOffice.
Home | LibreOffice - Free Office Suite - Based on OpenOffice - Compatible with Microsoft

However, you mention CSV files and these are not actually Excel Spreadsheets, they can just be viewed in a text editor if needs be, or any Spreadsheet software will open a formatted view.  There are also CSV specific viewers such as Nirsoft's
CSV / Tab delimited file viewer and converter for Windows (nirsoft.net)
 

I hadn't heard of that %SQL method either and, as well as speed, the %File method has advantages such as more file details being returned and better filtering with wildcards.

Hi, apologies, I missed that, the fix is now merged.

BTW, do you have an example of the OS commands output when this fails?