ConversationHandler not moving to the next state

I have the following ConversationHandler

conv_handler = ConversationHandler(
        entry_points=[CommandHandler('entry' entry)],
        states={
            ONE: [MessageHandler(filters.TEXT, one)],
            TWO: [MessageHandler(filters.TEXT, two)],
            THREE: [CallbackQueryHandler(three)],
            FOUR: [CallbackQueryHandler(four)]
        },
        fallbacks=[CommandHandler(Commands.CANCEL.value, cancel)],
    )

I defined the states keys as follows: ONE, TWO, THREE, FOUR = range(4)

Entry function:

async def entry(update: Update, context: ContextTypes) -> int:
    await update.message.reply_text("bla")
    return ONE

ONE function:

async def one(update: Update, context: ContextTypes) -> int:
    x = update.message.text
    await update.message.reply_text("yes. bla.")
    context.user_data["x"] = x
    return TWO

TWO function:

async def two(update: Update, context: ContextTypes) -> int:
    await update.message.reply_text("bla")
    keyboard = [
        ['7', '8', '9'],
        ['4', '5', '6'],
        ['1', '2', '3'],
        ['0']
    ]

    await update.message.reply_text("bla", reply_markup=InlineKeyboardMarkup(keyboard))
    query = update.callback_query
    await query.answer()
    context.user_data["x"] = query.data
    return THREE

The transition between the entry function to ONE works, but the next transition between ONE and TWO doesn't.

While debugging, when I am about to return ONE, the object self.map_to_parent is None so I suppose there was somewhat of a parsing error (?) in the ConversationHandler but I can't find it.

Additional info:

• No errors displayed
• python-telegram-bot = "==20.0a1"

source https://stackoverflow.com/questions/73838709/conversationhandler-not-moving-to-the-next-state