If your Excel spreadsheet file isn't showing in the folder, this may be because you've saved it in a different file format. 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.
Also, if you're using OneDrive, ensure that your file resides in the main OneDrive folder. Files stored in subfolders can prevent Geckoboard from accessing it.
Tip
If after converting to .xlsx your file still isn't listed, try searching for it by typing its name in the Search field.