The shared workbook has been saved in a file format that is recognized by earlier versions of Excel. To keep this workbook ...

The shared workbook has been saved in a file format that is recognized by earlier versions of Excel. To keep this workbook synchronized with changes that other shared workbook users make, you need to close and reopen the workbook.  • Click OK to close and reopen the workbook in Compatibility mode. • Click Cancel to view the workbook as read-only.