Why can't I launch Youtube player?

Question

Android

I use Youtube API to embed the player in the application.

package com.ktvray.mobile.videoPage;

import android.content.Context;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.support.v7.app.AppCompatActivity;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MenuItem;
import android.view.View;

import com.google.android.youtube.player.YouTubeInitializationResult;
import com.google.android.youtube.player.YouTubePlayer;
import com.google.android.youtube.player.YouTubePlayerSupportFragment;



public class ContentVideoPage extends AppCompatActivity {

    private YouTubePlayer YPlayer;

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        int id = item.getItemId();
        if (id == android.R.id.home) {
            onBackPressed();
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.fragment_video_content);
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        getSupportActionBar().setHomeButtonEnabled(true);
        Bundle args = getIntent().getExtras();
        final String video_id = (String) args.get("video_id");
        YouTubePlayerSupportFragment youTubePlayerFragment = YouTubePlayerSupportFragment.newInstance();
        FragmentManager fragmentManager = getSupportFragmentManager();
        FragmentTransaction transaction = fragmentManager.beginTransaction();
        transaction.add(R.id.youtube_fragment, youTubePlayerFragment).commit();
        youTubePlayerFragment.initialize("AIzaSyXXXXXXXXXXXXXXXXXXXX", new YouTubePlayer.OnInitializedListener() {
            @Override
            public void onInitializationSuccess(YouTubePlayer.Provider arg0, YouTubePlayer youTubePlayer, boolean b) {
                if (!b) {
                    YPlayer = youTubePlayer;
                    YPlayer.loadVideo(video_id);
                    YPlayer.play();
                }
            }

            @Override
            public void onInitializationFailure(YouTubePlayer.Provider arg0, YouTubeInitializationResult arg1) {
                // TODO Auto-generated method stub
            }
        });
    }
}

On one of the test devices, it says "Failed to start the Youtube player."
LG p970
What could it be?