Setting up OAuth 2.0 - What does this error mean: Invalid client

This article is part of the article serie Setting up OAuth 2.0 - Introduction

This error is shown when the re-direct URL in the GET for acquiring the authorization code is different than the re-direct URL that is registered on the client ID. These URL's should always be the same. This means that the URL needs to be changed.

Solution
Change the redirect URL in the GET equal to the registered redirect URL, this can easily be done in the developers portal.

In some cases the error will be shown when an incorrect client secret is used. This client secret can be renewed within the developer portal as referenced above.