A content app does not launch unless you configure an action bar. This is too much to ask. When you configure your first content app step-by-step, you have to create a lot of configuration before you can see the app run for the first time.

1. Configure the app classes
2. Add the app to the launcher
3. Configure a browser subapp
4. Configure a workbench
5. Add columns to the workbench
6. Configure actions
7. Configure an action bar

Make the threshold lower. Give new users the "whoa it works" feeling faster. Make the app launchable after step 3. Even if it just displays an empty subapp.

The system can handle a missing actionbar definition already today.

WARN: No actionbar definition found. This will result in an empty action bar. Is that intended?

So maybe it is just the configured content app that fails to start.