Unity 5.5.4p4 with GPG for Unity crash on authentication

I’m using the latest personal Unity version, together with the latest version of GPG for Unity from Github. The moment I click Login or let the GPG login during start, my game crashes.

I’ve searching and tried so many things.
What i’ve done so far:

  • Downgraded the sdk tool to 25.2.3/.5
  • Downgraded the plugins to play-services-*-10.0.1
  • Different way of using the authentication part.
    So far nothing worked for me.

My leaderboard code is the following:

using UnityEngine;
using System.Collections;
using GooglePlayGames;
using UnityEngine.SocialPlatforms;
using UnityEngine.UI;
using GooglePlayGames.BasicApi;

public class Leaderboard : MonoBehaviour
    #region PUBLIC_VAR
	public string leaderboard;

	void Awake()
		Debug.Log ("!!! init");
		//PlayGamesPlatform.DebugLogEnabled = true;
	void Start ()
		Debug.Log("!!! Login called");
		Social.localUser.Authenticate((bool success) =>
			if (success)
				Debug.Log("Login Sucess");
				Debug.Log("Login failed");

Does anyone have a suggestion what to do next?
My game is available in Google Play Store under closed Alpha (with my email/account added).
I’m testing on my own device.

I’ve tried so many things and already lost more than a day to get this to work.

Maybe this will help you fix that error: