When trying to open or edit an Excel file in MS Office, many users report the error “Excel cannot open the file because the file format or extension is invalid.”
The full error message is as follows:
“Excel cannot open the file `Filename.xlsx` because the file format or extension is invalid. Make sure the file is not damaged and that the file extension matches its format.”
The error message `Document format and file extension do not match’ when a user attempts to open certain files in Microsoft Office, including Microsoft Excel. All previously saved data will be deleted when you click the “Yes” button.
In this article, we will explain the common causes of this error and discuss some effective solutions to fix the .xlsx error. We will also explain to you how to recover MS Excel data.