How to Recover a Microsoft Excel File That Is Not in a Recognizable Format. If Microsoft Excel fails to recognize a file in the XLSX or XLS format, the data contained in the file could be corrupted.

Opening XLSM Files in Excel By default, you should be able to open an XLSM file without an issue (as long as you're using Excel 2007 or later), but the macros normally aren't enabled by default.

If you can't open a file on your computer, don't give up right away. These tricks will give you a fighting chance of accessing or recovering its contents.