What does the message “Unable to open xlsx file format or as its extension is not valid” mean when opening a file generated by MyReport Messenger?

The message “Unable to open xlsx file format or as its extension is not valid” Verify the file is not damaged,and that 
the extension matches the format of the file is displayed at the opening of a file generated by MyReport Messenger 
when the source file contains too many characters (e.g. spaces after the extension of the source file).