join.html에서 회원 가입하면 not found로 넘어갑니다.

회원가입페이지 만들기 부분에서 not found 오류가 납니다.

    {% with messages = get_flashed_messages() %}
        {% if messages %}
            <script>
                alert('{{messages[-1]}}');
            </script>
        {% endif %}
    {% endwith %}

    <div class="join_container">
        <form action="form" method="POST" action="/join">
            <div class="form_group">
                <label for="name">이름</label>
                <input type="text" name="name" id="name">
            </div>
            <div class="form_group">
                <label for="email">이메일</label>
                <input type="text" name="email" id="email">
            </div>
            <div class="form_group">
                <label for="pass">비밀번호</label>
                <input type="password" name="pass" id="pass">
            </div>
            <div class="form_group">
                <label for="pass2">비밀번호 확인</label>
                <input type="password" name="pass2" id="pass2">
            </div>
            <div class="form_group">
                <input type="submit" value="가입하기">
            </div>                          
        </form>
    </div>

@app.route('/join', methods=['GET', 'POST'])
def member_join():
    if request.method == 'POST':
        name = request.form.get('name', type=str)
        email = request.form.get('email', type=str)
        pass1 = request.form.get('pass', type=str)
        pass2 = request.form.get('pass2', type=str)

        if name == '' or email == '' or pass1 == '' or pass2 == '':
            flash('입력되지 않은 값이 있습니다.')
            return render_template('join.html')

        if pass1 != pass2:
            flash('비밀번호가 일치하지 않습니다.')
            return render_template('join.html')

        members = mongo.db.members
        cnt = members.find({'email': email}).count()
        if cnt > 0:
            flash('중복된 이메일 주소입니다.')
            return render_template('join.html')

        current_utc_time = round(datetime.utcnow().timestamp() * 1000)
        post = {
            'name': name,
            'email': email,
            'pass': pass1,
            'joindate': current_utc_time,
            'logintime': '',
            'logincount': 0,
        }

        members.insert_one(post)

        return ''
    else:
        return render_template('join.html')

<form action="form" method="POST" action="/join">