The executable python file outputs fatal error message

I have written a python script that communicates with the web page and makes an online order. In addition to that I have added some GUI, which allows the user to select the day of the order. Here is the python script

import easygui
import sys
from selenium import webdriver
from selenium.webdriver.common.keys import Keys
from selenium.webdriver.support.ui import WebDriverWait
from selenium.common.exceptions import TimeoutException 
from selenium.webdriver.support import expected_conditions as EC
from selenium.webdriver.common.by import By
from selenium.webdriver.support.ui import Select

import tkinter as tk
import tkinter.font as tkFont




badge_number = 111111

# Widget pop up for selection of the order day 
root = tk.Tk()
def center_window(w=300, h=200):
    # get screen width and height
    ws = root.winfo_screenwidth()
    hs = root.winfo_screenheight()
    # calculate position x, y
    x = (ws/2) - (w/2)    
    y = (hs/2) - (h/2)
    root.geometry('%dx%d+%d+%d' % (w, h, x, y))

root.geometry("400x450")

Label = tk.Label(root, text = "Select lunch Order Day", font = ("Helvetica", 15))
Label.pack(pady=50, padx=40)

helv15 = tkFont.Font(family = "Helvetica", size = 15)
root.lift()
v = tk.StringVar()
v.set("Today")
tk.Label(root, textvariable = v).pack()

def close_window(): 
    root.destroy()



today = tk.Radiobutton(root, text = "Today", variable = v, value = "Today", font = helv15).pack()
tomorrow = tk.Radiobutton(root, text = "Tomorrow", variable = v, value = "Tomorrow", font = helv15).pack()
cancel = tk.Radiobutton(root, text = "Cancel", variable = v, value = "Cancel", font = helv15).pack()
submit = tk.Button(root, text = "Submit", command = close_window, font = helv15).pack()



center_window(400, 400) 

root.mainloop()

if v.get() == "Cancel":
    sys.exit("Ordering was terminated")



driver = webdriver.Chrome(executable_path = "C:\webdrivers\chromedriver.exe")
driver.get("http://web_page/")

element = driver.find_element_by_name('employee_id')
element.send_keys(badge_number)


driver.find_element_by_xpath("/html/body/section/header/form/div/button").click()

# /html/body/section/header/form/div/button
delay = 60



todayBut = "/html/body/section/div[1]/div[2]/div/div/div/span[2]/span[1]/form/button"
tomorBut = "/html/body/section/div[1]/div[2]/div/div/div/span[1]/span[1]/form/button"
favorButToday = "/html/body/section/div/div[1]/button"
favorButTomor = "/html/body/section/div/div[1]/button/a"
myFavOrderID = "fav_order_view"


try:
    element = WebDriverWait(driver, 10).until(
        EC.visibility_of_element_located((By.XPATH, todayBut)))
except TimeoutException:
    print ("Loading Day Selection page took too much time!")


if v.get() == "Today":
    driver.find_element_by_xpath(todayBut).click()

    #favorite choice 
    try:
        element = WebDriverWait(driver, 10).until(
        EC.visibility_of_element_located((By.XPATH, favorButToday)))
        driver.find_element_by_xpath(favorButToday).click()
        try:
            element = WebDriverWait(driver, 10).until(
            EC.visibility_of_element_located((By.ID, myFavOrderID)))
            driver.find_element_by_id(myFavOrderID).click()

            ### select floor, order date and order now       
            select_floor = Select(driver.find_element_by_name("floor_number"))
            select_floor.select_by_index("9")
            select_day = Select(driver.find_element_by_name("order_date"))
            select_day.select_by_value("today")
            orderNowBtn = "/html/body/div[1]/div[2]/div/div/div[3]/form/button"
            driver.find_element_by_xpath(orderNowBtn).click()
            print("Today's order was successfully made!")
        except TimeoutException:
            print ("Loading Favorites page took too much time!")
    except TimeoutException:
        print ("Loading took too much time!")

else:

    driver.find_element_by_xpath(tomorBut).click()

    #favorite choice 
    try:
        element = WebDriverWait(driver, 10).until(
        EC.visibility_of_element_located((By.XPATH, favorButTomor)))
        driver.find_element_by_xpath(favorButTomor).click()
        try:
            myFavOrderIDTomor = "fav_order_view"
            element = WebDriverWait(driver, 10).until(
            EC.visibility_of_element_located((By.ID, myFavOrderIDTomor)))
            driver.find_element_by_id(myFavOrderIDTomor).click()

            ### select floor, order date and order now       
            select_floor = Select(driver.find_element_by_name("floor_number"))
            select_floor.select_by_index("9")
            select_day = Select(driver.find_element_by_name("order_date"))
            select_day.select_by_value("tomorrow")
            orderNowBtnTomor = "/html/body/div[1]/div[2]/div/div/div[3]/form/button"
            driver.find_element_by_xpath(orderNowBtnTomor).click()
            print("Tomorrow's order was successfully made!")
        except TimeoutException:
            print ("Loading Favorites page took too much time!")
    except TimeoutException:
        print ("Loading took too much time!")

However, I wanted to have it as an .exe file to run it with just double-click from my desktop. So, I have installed pyinstaller from git and run the simple line in the cmd (pyinstaller.exe --onefile --windowed --icon=app.ico LunchOrder.py). Unfortunately, the .exe isn't doign anything, it just pops up the "Fatal error detected" message, without any GUI (that I have written into the script itself). Any help would be appreciated!