Table separator lines not displaying correctly in tk

Table separator lines are not displayed. I need separator lines between rows and columns. What is the problem?

  def show_submenu_102(self):
    # creat manager Fiscal year
        sub_102 = tk.Toplevel(self.root)
        sub_102.title("Fiscal year management")
        sub_102.geometry("560x320")
        sub_102.configure(bg="#9fe1fd")
        sub_102.focus_force()

    # Create a blue box for buttons (150 pixels wide)
        blue_frame = tk.Frame(sub_102, bg="#9fe1fd", width=150, height=500)
        blue_frame.place(relx=0.99, rely=0, anchor="ne")

    # Create a white box with a distance from the right side of the blue box
        white_frame = tk.Frame(sub_102, bg="white", width=600, height=400)
        white_frame.place(relx=0.01, rely=0.01, anchor="nw")

    #  Headlines
        columns = ("Active", "Tax Percentage", "Fiscal Year", "Row")
        tree = ttk.Treeview(white_frame, columns=columns, show="headings")
        for col in columns:
            tree.heading(col, text=col , anchor="center")
            tree.column(col, width=100, anchor="center" , stretch=False)  # Adjust column width
        tree.pack(fill="both", expand=True)

    # Table settings
        style = ttk.Style()

        style.theme_use("default")

        style.configure("Treeview",
                        background="white",
                        foreground="black",
                        rowheight=25,
                        font=('Arial', 10),
                        fieldbackground="white",
                        bordercolor="black",  # Border color
                        borderwidth=2,        # Outer rim thickness
                        highlightthickness=2, # Thickness of internal dividing lines
                        highlightcolor="black" #Color of the dividing lines
                        )
    
    # Column capital configuration
        style.configure("Treeview.Heading",
                        background="#9fe1fd",
                        foreground="black",
                        font=('Arial', 12, 'bold'),
                        relief="flat"  # Remove prominence
                        )
    
    # Activating internal dividing lines
        style.layout("Treeview", [
            ('Treeview.treearea', {'sticky': 'nswe', 'border': 1})
            ])
        #_____________________________

    # Function to load fiscal years from the database and display in a table
        def load_financial_years():
           conn = sqlite3.connect('tanbal.db')
           cursor = conn.cursor()

           try:
           # Checking the existence of a table
 financial_years
               cursor.execute("SELECT name FROM sqlite_master WHERE type='table' AND name='financial_years'")
               if cursor.fetchone():
               #Getting fiscal years from a table
                   cursor.execute("SELECT year, tax_rate, is_default FROM financial_years")
                   years = cursor.fetchall()

               # Clearing the table and adding new years
                   tree.delete(*tree.get_children())
                   for index, (year, tax_rate, is_default) in enumerate(years, start=1):
                       tree.insert("", "end", values=("Active" if is_default else "Inactive", tax_rate, year, index))
               else:
                   print("The financial_years table does not exist.")
           except sqlite3.Error as e:
               print(f"Error loading fiscal years: {e}")
           finally:
               conn.close()

    # Calling the function to load fiscal years
        load_financial_years()

 # The rest of the functions are sub-sets.

    # Creating buttons in a blue box
        add_button = tk.Button(blue_frame, text="Add", command=add_function, bg="white", fg="black")
        add_button.pack(pady=10)

        edit_button = tk.Button(blue_frame, text="edite", command=edit_function, bg="white", fg="black")
        edit_button.pack(pady=10)

        delete_button = tk.Button(blue_frame, text="delete", command=delete_function, bg="white", fg="black")
        delete_button.pack(pady=10)

        choice_button = tk.Button(blue_frame, text="select", command=choice_function, bg="white", fg="black")
        choice_button.pack(pady=10)

        move_button = tk.Button(blue_frame, text="Carryover to next year", command=move_function, bg="white", fg="black")
        move_button.pack(pady=20)

    #Create an exit button in a blue box
        exit_button = tk.Button(blue_frame, text="Esc", width=10, height=2, command=lambda: [self.root.focus_force(), sub_102.destroy()])
        exit_button.pack(pady=5)

    # Keyboard shortcuts
        sub_102.bind('<Insert>', lambda event: add_function())
        sub_102.bind('<Escape>', lambda event: [self.root.focus_force(), sub_102.destroy()])
        sub_102.bind('<F2>', lambda event: edit_function())
        sub_102.bind('<Control-Delete>', lambda event: delete_function())