When the Excel file becomes corrupt, start by creating a backup of the original file before performing any type of repair on it. Open Excel and then File -> Open -> Browse, select the corrupt workbook, click on the arrow button near the open button and select 'Open and Repair'. Try using Repair first and then use Extract Data if the repair does not work. You can also check an old copy or previous version to help you out. If the workbook is still not opening, you can use data recovery tools like Notchox to recover the documents from supported devices.