That error means either that you've misconfigured the app or that the authentication call is incorrect.

Note that `stackexchange.com/oauth/login_success` is not a valid `redirect_uri` irregardless.

You probably want/need to use **Client side** (Implicit) authentication, in which case the `redirect_uri` would be:

          `https://stackexchange.com/oauth/login_success`

Note the **mandatory** `https://`.

Be sure your app is configured as shown in [this answer][1].

Then you can use a URL like the following to authenticate:

    https://stackexchange.com/oauth/dialog?client_id={YOUR CLIENT ID}&scope=no_expiry&redirect_uri=https://stackexchange.com/oauth/login_success

When you fetch that page, something like this will end up as the redirected-to URL:

    https://stackexchange.com/oauth/login_success#access_token=wdR8Lm7m4ibD48lfrCcFxQ))&expires=86399

You would then use the `access_token` to make an API query like:

    https://api.stackexchange.com/2.2/questions/30028657/answers?site=stackoverflow&key=RoZwtHUrhMP088oVGCMlxA((&access_token=wdR8Lm7m4ibD48lfrCcFxQ))&filter=!)4k-FmUi-xgG3sdSdPz*cQNNqR0A

(Note that the example token, above, has long since been invalidated.  Use your own values for it and for `key`.)

  [1]: https://stackapps.com/a/6679/7653