[iOS] Integrated UnityAds not launching the defined callback

EDIT: solved in the thread linked by @LSTGames.

Since updating to Unity 5.5.0p3 (from 5.4.0f1), UnityAds won't launch any callback after the video shows up. I already tried to disable and re-enable UnityAds in the Services tab and regenerating Library folder, with no success. This is my code:

Code (CSharp):

1. public void LaunchAd () {
2.        ShowOptions options = new ShowOptions {resultCallback = OnVideoCallback};
3.        Advertisement.Show("rewardedVideoZone",options);
4. }
5. public void OnVideoCallback (ShowResult result) {
6.        Debug.Log("Ad finished");
7.        //more stuff here
8. }

The ad shows fine, but "Ad finished" never gets logged. The problem happens on iOS; in the editor the callback fires correctly; I haven't tried this yet on Android. Am I missing something in 5.5?

 

I had the same problem on Android, read more here: https://forum.unity3d.com/threads/rewarded-video-no-callback-on-android.449970/