[BNPL] Klarna / Affirm - No error message is displayed on the block checkout when the transaction is denied

[a-danae]

Describe the bug

When the transaction is denied by Klarna, the shopper is redirected to the checkout page but no error message is displayed.

This could be happening for Afterpay and Affirm too.

To Reproduce
Steps to reproduce the behavior:

1. Check out the branch add/klarna-payment-method
2. Make sure the currency store is USD, the Legacy checkout experience is disabled, and that Klarna is enabled
3. Ensure a page using the block checkout is selected as the default checkout page in WooCommerce, under Page setup > Checkout page, at /wp-admin/admin.php?page=wc-settings&tab=advanced
4. As a shopper, add a product to the cart, and go to the checkout page
5. In Klarna, log in with the following email address or phone number to get your transaction denied customer+denied@email.us or +13106354386
6. Select Pay now and continue. You'll get a "Sorry, we couldn't approve this purchase" error
7. Select Pay in 4 and continue. You'll get another error message
8. Click on "Return to checkout"
9. Notice that you go back to the store, but no error message is displayed. On the Stripe logs, you'll see the following entries

Error when processing payment: Customer was declined by Klarna
Error: We're not able to process this payment. Please try again later.

Expected behavior
The shopper must have a user-friendly message when returning to the checkout page.

[wjrosa]

The same issue happens with Affirm. See this comment. PR integrating Affirm here.

[wjrosa]

This seems to be a regression on woocommerce/woocommerce#42787 (comment) (see my comment).

This was first reported in Automattic/woocommerce-payments#7792 for Giropay (moved here, then here). Supposed fixed here.

I pinged the Rubik team there, so I will be closing this since it is not specific to BNPL.