Conflict: terminated by other getUpdates request; make sure that only one bot instance is running

This happens when 2 different clients send getUpdates method to Telegram servers for one bot token.

You should make sure you’re not running your script more than once at the same time, or your bot token is not used somewhere else.

If you’re certain that your script is executing alone and there are no other instances, then revoke your bot token from https://t.me/botfather and get a new token.

I fix this issue arranging code like this :

from telegram.ext import CommandHandler, Updater
from logging import basicConfig, getLogger, INFO

basicConfig(level=INFO)
log = getLogger()

def start(update, context):
    update.message.reply_text(
        "start this bot",
        parse_mode="markdown")

def help(update, context):
    update.message.reply_text(
        "help for this bot",
        parse_mode="markdown")

def main():
    updater = Updater(token=BOT_TOKEN, use_context=True)
    dispatcher = updater.dispatcher

    start_handler = CommandHandler("start", start)
    help_handler = CommandHandler("help", help)

    dispatcher.add_handler(start_handler)
    dispatcher.add_handler(help_handler)
    updater.start_polling()

if __name__ == '__main__':
    main()

If you are using flask, do not set debug mode to true also on your development server, first call main function then call flask server like this:-

app = Flask(__name__)

if __name__ == '__main__':
    main()
    app.run()

Stop the bot, close your IDE, make sure that all python processes were ended in the task manager, and try again.
That has helped me.