flet python does not work

[tarovq]

import flet as ft
import sqlite3

def fetch_data(table_name):
connection = sqlite3.connect('post_office.db')
cursor = connection.cursor()
cursor.execute(f"SELECT * FROM {table_name}")
rows = cursor.fetchall()
cursor.execute(f"PRAGMA table_info({table_name})")
columns_info = cursor.fetchall()
column_names = [col[1] for col in columns_info]
connection.close()
return column_names, rows

def add_customer(initials, adress, phone, email):
connection = sqlite3.connect('post_office.db')
cursor = connection.cursor()
cursor.execute("INSERT INTO Customers (Initials, Adress, Phone, Email) VALUES (?, ?, ?, ?)",
(initials, adress, phone, email))
connection.commit()
connection.close()

def main(page: ft.Page):
page.title = "Post Office Management System"
page.bgcolor = '#ebebeb'
page.window_maximized = True

initials = ft.TextField(label="Initials")
adress = ft.TextField(label="Adress")
phone = ft.TextField(label="Phone")
email = ft.TextField(label="Email")
add_customer_button = ft.Button(text="Add Customer", on_click=lambda e: add_customer(
    initials.value, adress.value, phone.value, email.value))

page.add(initials, adress, phone, email, add_customer_button)

page.run()

ft.app(target=main)
when I run the code, nothing happens and so with any code where there is import flet as ft