Geckoboard only supports the .xlsx file extension for Excel files. As a result, any .xls or .xlsm files won't be listed in your folder.
You'll need to save your workbook again as an .xlsx file type. If you're unsure on how to this, follow this guide to saving a workbook in another file format.
Tip
If after converting to .xlsx your file still isn't listed, try searching for it by typing its name in the Search field.
