for some reallly odd reason css doesen't apply

Question

I am currently writing a program that makes you go to a website without actually going to the website but for some odd reason CSS just doesn't work

from flask import Flask, request, session, Response
import random
import requests
import string
from tld import get_tld
import json
app = Flask(__name__)
app.secret_key = 'fjwefjwefjwe'
urls = {}

def turn_headers_to_dict(headers):
    return {"User-Agent":headers["User-Agent"]}
def generatetoken(l):
    return ''.join(random.choice(string.ascii_uppercase + string.digits) for i in range(l))

@app.errorhandler(404)
def gotowebsite(error):
    global urls
    print(urls)
    if not session.get('computer_id'):

        session['computer_id'] = generatetoken(100)
        urls[session['computer_id']]="https://www.google.com"
    else:
        print(session['computer_id'])
    print(urls)
    site = urls[session['computer_id']] + request.full_path
    print(site)
    header = turn_headers_to_dict(request.headers)
    if request.method == "GET":
        a= requests.get(site, headers=header)
    else:
        a =  requests.post(site,headers=header, data=request.form)
    return Response(a.content
    , mimetype="text/plain")
@app.route('/')
def index():
    global urls
    print(urls)
    print(session.get('computer_id'))
    if not session.get('computer_id'):
        print("doing")
        session['computer_id'] = generatetoken(100)
        urls[session['computer_id']]="https://www.google.com"

    else:
        try:
            urls[session['computer_id']]
        except:
            session['computer_id'] = generatetoken(100)
            urls[session['computer_id']]="https://www.google.com"
        print(session['computer_id'])
    print(urls)
    site = urls[session['computer_id']]
    print(site)
    header = turn_headers_to_dict(request.headers)
    a = requests.get(site, headers=header)

    return a.content

@app.route("/change/<url>")
def change(url):
    try:
        session['computer_id'] = generatetoken(100)
        urls.update({session['computer_id']:"https://"+url})
        print(urls)
        return "ok"
    except:
        return "error"
    
app.run()

i expected for it to be working flawlessly but for some reason CSS DOESENT WORK! WHYYYYY??? even JS works and i forgot to mention when i tweak the CSS a little bit IT STARTS TO WORK