Python telegram bot doesn't recognize text message – Telegram API

Here I have a code for making a simple echo bot for telegram.

from telegram.ext import Updater, CommandHandler, MessageHandler, Filters
import logging

from data.constants import API_TOKEN, LOGGING_FORMAT

logging.basicConfig(format=LOGGING_FORMAT, level=logging.DEBUG)

updater = Updater(token=API_TOKEN)
dispatcher = updater.dispatcher


def start(update, context):
    context.bot.send_message(chat_id=update.effective_chat.id,
                             text='Hello, dude.')


def echo(update, context):
    context.bot.send_message(chat_id=update.effective_chat.id,
                             text=update.message.text)


start_handler = CommandHandler('start', start)
echo_handler = MessageHandler(Filters.text, echo)


dispatcher.add_handler(start_handler)
dispatcher.add_handler(echo_handler)


if __name__ == '__main__':
    updater.start_polling()
    updater.idle()

I used a python-telegram-bot library for that.

For some reason, this bot recognizes only commands, but not plain text. I mean, the echo function echoes me only text, started from /. The function start works as it should.
The more interesting thing, that the same problem I had with another telegram-bot library – aiogram.

After got crazy I wrote to python-telegram-bot support to ask advice in solving my problem.
After running my snippet, support admitted, that it works fine for them and advice me last-hope-move: to try it on a new bot. I got new API key from @BotFather, tried it out, but now I’m here. That means my code still doesn’t work properly.

There’re some references, that could help us to solve it:

https://python-telegram-bot.readthedocs.io/en/latest/telegram.html
https://github.com/python-telegram-bot/python-telegram-bot/wiki/Extensions-–-Your-first-Bot

But I suppose, that the problem is in my working environment, despite I tried to run my code on different fresh device.