It is strongly recommended to use a test environment where changes can be made before making them on your live site. Some hosting services offer staging features, and you can also clone your website via plugins like Duplicator or WP Staging.
Regularly backing up your store is highly recommended and can lower downtime if a change is made that breaks or otherwise hinders the normal functioning of your site.
Make sure that you have enabled pretty permalinks in your WordPress installation. Otherwise callbacks from Klarna back to your store won’t work and orders will not be updated with the correct order status/information.
To get the order total to match between WooCommerce and Klarna you need to configure WooCommerce to display prices with 2 decimals. More information about displaying of prices and how it can cause rounding issues can be found in this article.
The plugin and Klarna only handle product quantity that is specified as an integer. For instance you can’t send 1.5 as the product quantity to Klarna. If you sell products where you charge by length or dimension we recommend that you use the Measurement Price Calculator plugin.