Can't receive frame Opencv Python Raspberry Pi

Question

I am working on Raspberry Pi 4 with the latest os VERSION="12 bookworm" and a Raspberry Pi camera Rev1.3. I want to use this pi camera to capture video useing opencv.

Issue: I getting error that Can't receive frame or in other words it can't access pi camera.It works fine with USB webcam but not with pi camera.

Here is the sample code:

import numpy as np
import cv2 as cv
cap = cv.VideoCapture(0)
if not cap.isOpened():
    print("Cannot open camera")
    exit()
while True:
    # Capture frame-by-frame
    ret, frame = cap.read()
    # if frame is read correctly ret is True
    if not ret:
        print("Can't receive frame (stream end?). Exiting ...")
        break
    # Our operations on the frame come here
    gray = cv.cvtColor(frame, cv.COLOR_BGR2GRAY)
    # Display the resulting frame
    cv.imshow('frame', gray)
    if cv.waitKey(1) == ord('q'):
        break
# When everything done, release the capture
cap.release()
cv.destroyAllWindows()

I have tried a few things:

1. I have tried this code with USB webcam and it workes fine with it.
2. I have updated /boot/config.txt or /boot/firmware/config.txt with the camera module code dtoverlay=ov5647
3. I have tried a new purchased camera of same version just to confirm that there is no issue in camera or connection.
4. I have tried libcamera-hello command on terminal that works fine, it opens up camera for a few seconds.

But this camera is not detected with the opencv. I have tried one other thing that might or might not helpfull to undestand the issue:- I tried to wisit https://webcamtests.com/ and same here it can detect USB camera but not the pi camera v1