cs50 web pset 1 中的登录表单根本不起作用（使用烧瓶）

我正在尝试创建一个登录表单，通过用户名和密码检查帐户是否存在我已经尝试了一些东西，但似乎无法让它工作

<form id="signupform" action="{{url_for  ('login') }}" method="post">
        <div class="input-group input-group-lg">
            <input type="text" class="form-control" placeholder="Username" aria-describedby="sizing-addon1" name="username" >
          </div>


        <div class="input-group input-group-lg">
            <input type="password" class="form-control" placeholder="Password (8 chars min)" aria-describedby="sizing-addon1" name="password" " >
          </div>


        <small id="emailHelp" class="form-text text-muted">
            We'll never share your info with anyone else.<br>
            <a href="signuppage">    No account? sign up here!</a>
        </small>

        <button type="button" class="btn btn-primary">Login</button>

    </form>

这是表格^^

import os

from flask import Flask, session ,render_template , request
from flask_session import Session
from sqlalchemy import create_engine
from sqlalchemy.orm import scoped_session, sessionmaker

app = Flask(__name__)

# Check for environment variable
if not os.getenv("DATABASE_URL"):
    raise RuntimeError("DATABASE_URL is not set")

# Configure session to use filesystem
app.config["SESSION_PERMANENT"] = False
app.config["SESSION_TYPE"] = "filesystem"
Session(app)

# Set up database
engine = create_engine(os.getenv("DATABASE_URL"))
db = scoped_session(sessionmaker(bind=engine))


@app.route("/")
def index():
    return render_template("login.html")


@app.route("/home" , methods=["POST"])
def login():

    # request username and password

    username=request.form.get("username")
    password=request.form.get("password")

    #check if account exists

    account= db.execute("SELECT * FROM users WHERE username = :username AND password = :password ",
    {"username":username , "password":password }).fetchone()

    if account is None:
        return render_template("loginerror.html")
    else:
        return render_template("homepage.html")

这是烧瓶应用程序^^

数据库也正确链接所以idk

我很迷茫，真的很感激任何帮助