Why does the Scheduled Report has nothing attached?
One of the possible reasons could be the column count exceeding the maximum limit of MS Excel (i.e. 255) Therefore, you will not be able to export to Excel as it is exceeding the Excel column limit of 255. If the data is more than the excel limit, then excel cannot handle and results in blank report. Make changes in the filter selection so that the column count does not cross the limit of 255.