Set 2Checkout hosted checkout page language for Paid Memberships Pro.

change-2co-locale.php

<?php
/**
 * Change the 2Checkout hosted checkout default language for Paid Memberships Pro WordPress Plugin.
 * Please see https://www.2checkout.com/documentation/checkout/parameter-sets/pass-through-products/ (Additional Parameters) for available languages.
 * 
 * You can add this recipe to your site by creating a custom plugin
 * or using the Code Snippets plugin available for free in the WordPress repository.
 * Read this companion article for step-by-step directions on either method.
 * https://www.paidmembershipspro.com/create-a-plugin-for-pmpro-customizations/
 */
function my_pmpro_change_2co_locale( $twoco_url, $order ) {
	$twoco_url .= '&lang=es_ib';
	return $twoco_url;
}
add_filter( 'pmpro_twocheckout_ptpstr', 'my_pmpro_change_2co_locale', 10, 2 );