Face detection not working in android studio

Question

I'm new to android studio and want to do face detection. The face detector code uses opencv and is written in python. I'm using chaquopy as the python SDK. When i run the app, the face is not detected. It is not showing any error also. Can someone help me out. Below is my MainActivity.java code:

public class MainActivity extends AppCompatActivity {

Button btn;
ImageView iv;


// now take bitmap and bitmap drawable to get image from image view
BitmapDrawable drawable;
Bitmap bitmap;
String imageString="";


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    btn = (Button)findViewById(R.id.submit);
    iv = (ImageView)findViewById(R.id.image_view);


    if(!Python.isStarted())
        Python.start(new AndroidPlatform(this));

    final Python py = Python.getInstance();


    btn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            // on click over button, get image from image view
            drawable = (BitmapDrawable)iv.getDrawable();
            bitmap = drawable.getBitmap();
            imageString = getStringImage(bitmap);
            // now in imagestring, we get encoded image string
            // now pass this input string to python script

            PyObject pyo = py.getModule("myscript");
            // calling the main function in python code and passing image string as parameter
            PyObject obj = pyo.callAttr("main", imageString);

            // obj will return value ie. our image string
            String str = obj.toString();
            // convert it to byte array
            byte data[] = android.util.Base64.decode(str, android.util.Base64.DEFAULT);
            // now convert it to bitmap
            Bitmap bmp = BitmapFactory.decodeByteArray(data, 0, data.length);

            //now set this bitmap to imageview
            iv.setImageBitmap(bmp);


        }
    });
}

// function to convert this image into byte array and finally into base 64 string
private String getStringImage(Bitmap bitmap) {
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    bitmap.compress(Bitmap.CompressFormat.PNG, 100, baos);
    // store in byte array
    byte[] imageBytes = baos.toByteArray();
    // finally encode to string
    String encodedImage = android.util.Base64.encodeToString(imageBytes, android.util.Base64.DEFAULT); // Base64.DEFAULT
    return encodedImage;

}

}

and the below shown is my python script "myscript.py"

import numpy as np
import cv2
import io
from PIL import Image
import base64
import face_recognition

def main(data):
    decoded_data = base64.b64decode(data)
    np_data = np.fromString(decoded_data, np.uint8)
    img = cv2.imdecode(np_data, cv2.IMREAD_UNCHANGED)
    img_rgb = cv2.cvtColor(img, cv2.COLOR_BGR2RGB)
    img_gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
    face_locations =  face_recognition.face_locations(img_gray)
    for(top,right,bottom,left) in face_locations:
        cv2.rectangle(img_rgb, (left,top),(right,bottom),(0,0,255),8)
    # convert this image to PIL
    pil_im = Image.fromarray(img_rgb)
    #convert this image to byte
    buff = io.BytesIO()
    pil_im.save(buff, format="PNG")
    #converting to base64
    img_str = base64.b64encode(buff.getvalue())
    return ""+str(img_str, 'utf-8')

My minSdkVersion is 16 and targetSdkVersion is 30. I'm not understanding what is the problem with this code. Can someone help me. Thanks in advance.