OpenCV code opens a video but displays a blocked camera

I am learning how to display video using python 3 and OpenCV. I use PyCharm for my IDE. When I run the code to display a continuous video from my webcam, it just gives me the symbol of a blocked webcam. Later, the saved file of that "video" is in my documents but is useless. Do I just need to change the camera setting somewhere?

import numpy as np
import cv2

cap = cv2.VideoCapture(0)

# Define the codec and create VideoWriter object
fourcc = cv2.VideoWriter_fourcc(*'XVID')
out = cv2.VideoWriter('output.avi',fourcc, 20.0, (640,480))

while(cap.isOpened()):
    ret, frame = cap.read()
    if ret==True:
        frame = cv2.flip(frame,0)

        # write the flipped frame
        out.write(frame)

        cv2.imshow('frame',frame)
        if cv2.waitKey(1) & 0xFF == ord('q'):
            break
    else:
        break

# Release everything if job is finished
cap.release()
out.release()
cv2.destroyAllWindows()

Thanks in advance.