Turtle Library Screen Not Working Properly in Mac but Working in other systems

Question

I wanted to make a pong game in Python by using the Turtle library, but the output screen is not correct.

the output screen is like this.

But it should be like this

here is my code:-

import turtle

wn = turtle.Screen()
wn.title("Pong by Sameer")
wn.bgcolor("black")
wn.setup(width=800, height=600)
wn.tracer(0)

# Paddle A
paddle_a = turtle.Turtle()
paddle_a.speed(0)
paddle_a.shape("square")
paddle_a.color("white")
paddle_a.shapesize(stretch_wid=5, stretch_len=1)
paddle_a.penup()
paddle_a.goto(-350, 0)

# Paddle B
paddle_a = turtle.Turtle()
paddle_a.speed(0)
paddle_a.shape("square")
paddle_a.color("white")
paddle_a.shapesize(stretch_wid=5, stretch_len=1)
paddle_a.penup()
paddle_a.goto(350, 0)

while True:
    wn.update()