Pygame black screen issue [SOLVED]

I am learning python for a week and I get an issue.

So, my pygame window doesn't display any rectangle and doesn't cause any error. 

Can you tell me how to fix it? 

file name: Screenshot 2020-03-15 at 11.27.51 AM.png

https://imgur.com/a/1XFx7Go

import pygame
import sys

# General setup
pygame.init()
clock = pygame.time.Clock()

# Setting up the main window
screen_width = 1024
screen_height = 768
screen = pygame.display.set_mode((screen_width, screen_height))
pygame.display.set_caption('Pong')

# Game Rectangles
ball = pygame.Rect(screen_width / 2 - 15, screen_height / 2 - 15, 30, 30)
player = pygame.Rect(screen_width - 30, screen_height / 2 - 70, 10, 140)
opponent = pygame.Rect(30, screen_height / 2 - 70, 10, 140)

bg_color = pygame.Color('grey12')
light_grey = (200, 200, 200)

while True:
    # Handling input
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            pygame.quit()
            sys.exit()

    # Visuals
    screen.fill((255,0,0))
    pygame.draw.rect(screen, light_grey, player)
    pygame.draw.rect(screen, light_grey, opponent)
    pygame.draw.ellipse(screen, light_grey, ball)
    pygame.draw.aaline(screen, light_grey, (screen_width/2, 0), (screen_width/2, screen_width))

    # Updating the window
    pygame.display.flip()
    clock.tick(60)