>I tested the beta version 10 (on my PC). It works. The only thing I see differently (between this version and the previous one) is that the XLSX file created with Beta 10 does not show the vertical and horizontal lines separating the columns and rows. That is, the spreadsheet does not look like it has cells; but more like a report.
>Is this by design?

That is a new feature added to the method that was requested, to show or hide the cell lines. I added another parameter to the method, tlShowGridLines as the 6th parameter. Set this to True.