Cannot upload to an app ID though I have the correct permissions
Most likely, you are logged into Gmail under a different account. Go to Gmail, and click Sign Out. Then go to the developer console. It should ask you to log in or select from several accounts.
(I've been using appengine since 2009 and haven't needed support until now.) I've been added to a new project from the cloud console. When I try to upload the app, AppEngine launcher says "This application does not exist".  Furthermore, in Cloud console, nothing appears under the appengine heading.  At the same time, however, the old appengine.appspot.com DOES have the application listed. Any help?