Why does the App Designer produce an error message on packaging?

I have an app which i completed in one session. Tragically, the App weil not package and the App will not save and store . I have had to abandon the work, entirely. Incidently no such problem in the onlinwe version because there is no packaging provision or make-a-prj file for the app.

[Mario Malic]

There is no information for us to help you. Provide error message.