Why does the program return an empty response

This is my code in FLASK. I try to make validation form in flask library. also i try to check it with postman request. But it doesn't work, please help:

from flask import Flask
from flask_wtf import FlaskForm
from wtforms import StringField, IntegerField

app = Flask(__name__)
app.config['WTF_CSRF_ENABLED'] = False

class RegistrationForm(FlaskForm):
    email = StringField()
    phone = IntegerField()
    name = StringField()
    address = StringField()
    index = IntegerField()
    comment = StringField()


@app.route('/registration', methods=['POST'])
def registration():
    form = RegistrationForm()
    if form.validate_on_submit():
        email, phone = form.email.data, form.phone.data
        return fr"Successfully registered user {email} with phone +7{phone}"
    return f'Invalid input, {form.errors}', 400


if __name__ == '__main__':
    app.run(debug=True)

I try to make POST with postman, but it return: Successfully registered user None with phone +7None.

How can i fix that, please, help

Try to rewrite code, try to debug, but i didn't find that exception

Don't you have to pass the "request.form" object into the RegistrationForm() ?

I have always seen it done like this:

Replace:

form = RegistrationForm()

with:

form = RegistrationForm(request.form) 

You will also need to update

from flask import Flask

to:

from flask import Flask,request

If that doesn't work, go forward to the next debugging step:

Something is preventing the form variable from containing what you expect it to contain

Try this and report what it outputs. (Update your question, rather than putting the answer here, because you can correctly format it in the question, but not in a comment).

Add one line between these two lines. Change this:

    if form.validate_on_submit():
        email, phone = form.email.data, form.phone.data

... to this:

    if form.validate_on_submit():
        print(form)
        email, phone = form.email.data, form.phone.data