Most of the time, that error is because there's no application installed on the app ID, or there's no root handler.
For the first issue, go to
appspot.com, click on your application ID, then click on the Admin Logs link on the left side of the page:
http://imgur.com/a/UtX1M . On the resulting page, do you see any log lines that include the words "deploy" or "release"?
For the second issue, go to your application logs. Do you see any requests erroring out? If so, can you describe what those requests are and the error message included in the log?