No bonus is given for the referred user, how to solve?

Question

Python

Functions:

def referral_web(user_id, deposit_sum):
    conn = sqlite3.connect("base_ts.sqlite")
    cursor = conn.cursor()

    cursor.execute(f'SELECT * FROM users WHERE user_id = "{user_id}"')
    user = cursor.fetchone()

    if user[4] == '0':
        return
    else:
        info = profile(user_id)
        user2 = cursor.execute(f'SELECT * FROM users WHERE user_id = "{user[4]}"').fetchone()

        profit = int(info[5]) + int(10)

        balance = float(user[5]) + float(profit)

        cursor.execute(f'UPDATE users SET balance = {balance} WHERE user_id = "{user[4]}"')
        conn.commit()

        ref_log(user2[0], profit, user2[1])


def ref_log(user_id, profit, name):
    conn = sqlite3.connect("base_ts.sqlite")
    cursor = conn.cursor()

    cursor.execute(f'SELECT * FROM ref_log WHERE user_id = "{user_id}"')
    user = cursor.fetchall()

    if len(user) == 0:
        cursor.execute(f'INSERT INTO ref_log VALUES ("{user_id}", "{profit}", "{name}")')
        conn.commit()
    else:
        all_profit = user[0][1]

        all_profit = float(all_profit) + float(profit)

        cursor.execute(f'UPDATE ref_log SET all_profit = {all_profit} WHERE user_id = "{user_id}"')
        conn.commit()

Conclusion:

elif message.text == ' Referrals':
            bot_name = bot.get_me().username
            ref_code = func.check_ref_code(chat_id)
            bot.send_message(chat_id, f''' Get bonuses for invited friends.

 Send a link to a friend
https://t.me/{bot_name}?start={ref_code}

➕ 10$ for each friend you invite
➕ 10% of your friends' earnings

Earnings: {func.check_all_profit_user(chat_id)}$''')

When following a referral link, it does not protect the balance, how to solve?