Play store Beta Testing returning 404

I'm a developer and i was thrilled when I was watching Google IO 2013 and learned about the new Beta testing feature. So I created a Google+ community and a google group and placed the testers in there (me included).

All we get (the developers and testers) when we visit the https://play.google.com/apps/testing/com.package.stuff is this:

Is there any trick I am missing? I would really like to use this feature.

I know there are alternatives like https://testflightapp.com/ but I'd rather keep my app under this environment where I can "promote" the Beta apk to the Production phase and so on.

I had this same issue. The reason the link is not working is because the app must be published before the link will be active. I repeat the app must be published, this does not mean there must be an APK in production. On the top right of your applications developer console page there is a drop down menu that allows you to publish the app. That link will become active immediately and your app will be available in a few hours to your testers on the Play Store.