Cannot connect my mobile app to Dropbox API

Hello,

I'm developing an Android app that want to connect to Dropbox to allow user to upload some documents. I use the Dropbox SDK (version 5.0.0) here : https://github.com/dropbox/dropbox-sdk-java

Currently I'm stuck at the authorization process, when I call this function : 

Auth.startOAuth2Authentication(activity , dropbox_key);

I'm connecting to the Dropbox app installed on the device, and when i click on the "authorize" button, the app displays an error : 

This app has reached its user limit.
Contact the app developer and ask them to use the Dropbox API App Console to increase their app's user limit.

Except that the app has just been created in the Dropbox console and i'm connecting only one user for the test.

If I try outside of the Dropbox app (using web navigator) the authentication flow ends with an error 500 page.

I've checked the app key and secret, they are correct, and the configuration in the Dropbox Console has been finished.

I also tested with previous versions of the SDK, same error.

I'm out of solutions, am I missing something ?