Hi,

Try to extend like:

/** @odoo-module **/

import PaymentScreen from 'point_of_sale.PaymentScreen';

import Registries from 'point_of_sale.Registries';

import session from 'web.session';

import { PosLoyaltyCard } from '@pos_loyalty/js/Loyalty';

export const PosLoyaltyPaymentScreen = (PaymentScreen) =>

    class extends PaymentScreen {}

Hope it helps