Android : Android Picasso not loading all my images that I listed in my drawable

I have a problem with android picasso. Some images are not loading in my phone. It just display black page it differs from phone. Other phones load it all while others didn't load at all or some is missing.

I'm using adapter btw

Here's my adapter code

        package com.jc.jcpremiere;



import com.squareup.picasso.Picasso;
import android.content.Context;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.RelativeLayout;

    public class ViewPagerAdapter extends PagerAdapter {
        // Declare Variables
        Context context;
        int[] flag;
        String[] rank;
        LayoutInflater inflater;

        public ViewPagerAdapter(Context context,  int[] flag, String[] rank) {
            this.context = context;
            this.flag = flag;
            this.rank = rank;
        }

        @Override
        public int getCount() {
            return rank.length;
        }

        @Override
        public boolean isViewFromObject(View view, Object object) {
            return view == ((RelativeLayout) object);
        }

        @Override
        public Object instantiateItem(ViewGroup container, int position) {
            inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            View itemView = inflater.inflate(R.layout.app3x, container, false);
            ImageView imgflag = (ImageView) itemView.findViewById(R.id.items); // need this ImageView

            Picasso.with(context).load(flag[position]).resize(50, 50)
            .centerCrop().into(imgflag); // use ImageView
            //imgflag.setImageResource(flag[position]);
            ((ViewPager) container).addView(itemView);
            return itemView;
        }



        private ImageView findViewById(int items) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public void destroyItem(ViewGroup container, int position, Object object) {
            // Remove viewpager_item.xml from ViewPager
            ((ViewPager) container).removeView((RelativeLayout) object);

        }
    }