Ads initialize error

Hey guys,

I am getting following error on (and ONLY on) Nexus 5X on Google Pre-Launch-Report:

Code (csharp):

1. AndroidJavaException: java.lang.NullPointerException: Attempt to invoke interface method 'void com.unity3d.ads.IUnityAdsListener.onUnityAdsError(com.unity3d.ads.UnityAds$UnityAdsError, java.lang.String)' on a null object reference

My code for initializing Unity Ads:

Code (csharp):

1. public void Initialize()
2. {
3.     Advertisement.AddListener(this);
4.     Advertisement.Initialize(gameId, testMode);
5. }

This class inherits IUnityAdsListener, so that's not the problem.
I'm using Unity Ads 3.4.2 and Unity 2018.4.17f1 LTS.

Can anyone help?

 

And the listener is also not being added twice.

 

I'm having the same issue. And, somehow it got released into Production... >.<