‘Oops’ error
The ‘Oops’ error is most often caused by the Klarna API credentials not matching those in your Shopify store. Try copying and pasting them again from your saved credentials from the Klarna Merchant portal to both the alternative payment method(s) configuration and the Klarna Payments app in your Shopify store.

‘No available methods’ error
This means that the Klarna payment method you have on your store is not able to accept the order.

‘Not supported for this country’ error
This means that Klarna is not able to accept the order.

Fulfillment error email from Shopify
If you’ve received an email informing you that ‘A fulfillment action for Shopify order XXX/ Klarna order ID XXX for store NXXXXX has resulted in an error’, review the order in your Shopify admin tool and in the Klarna Merchant portal to determine the cause of the error.
The fulfillment error email notifies you that an order fulfillment has failed. This can be due to an order being expired or already captured in the Merchant portal.