How do I fix the error message “401 Unauthorised” in the checkout? | Klarna New Zealand

How do I fix the error message “401 Unauthorised” in the checkout?

Check the following:

If you use Klarna API-credentials for production, make sure that the test mode is switched off.
If you use Klarna API-credentials for our test environment, make sure that the test mode is switched on.
If the problem is still there please contact Merchant Support for further assistance.