Data publishing is stopped by the CMS if data errors are found in your project. Check each data tab and fix the errors. Once all your data errors are corrected, you will be able to publish to the app.
For example, if your session type says Social Events in the Agenda tab but it is listed as SOCIAL EVENTS or Social Event in the Types tab, there is a mismatch in your data. Correct your data so that the content matches exactly including upper/lower case, spaces used, and spelling.