WooCommerce EU VAT plugin relies on the Europa VIES service. But when it's down your customers get an annoying error and the order cannot be completed. This snippet provides a fix.

woocommerce-eu-vat-vies-offline-fix.php

<?pp

/*

  !!! Just a quick warning, if WooCommerce updates its plugin these changes will be gone !!!

  1) Find class-wc-eu-vat-number.php, it's located under wp-contents/plugins/woocommerce-eu-vat-number/includes
  2) Skim trough until you find line 160
  3) Do the following
*/

/* On line 160 you'll find this line of code */
return new WP_Error( 'api', sprintf( __( 'VAT API Error: %s', 'woocommerce-eu-vat-number' ), $response->get_error_message() ) );

/* Replace line 160 with the following */
if( strstr($response->get_error_message(), 'cURL error 28') !== false ){
    // fail silently and let order go through
    return true;
} else {
    return new WP_Error( 'api', sprintf( __( 'VAT API Error: %s', 'woocommerce-eu-vat-number' ), $response->get_error_message() ) );
}