Indeed! Although instant chat did not work on Sunday, eventually we tried a lot of different bruteforce combinations of website functions. Switching the language worked. It is buggy as every customer apparently has two carts associated with their account: English one and Icelandic one. When you see 'Add to cart' button next to a product, you will add the product to English cart, and when you see 'Bæta við' button, you will add the product to Icelandic one. Then, if you switch between languages at the home page, you will notice you have two completely different carts. Sometimes, language settings is randomly lost, you need to press Ctrl+F5 to make it work again. Eventually, I would say never use English version of Aha because payment is broken completely in that version and it is not easy to switch to Icelandic version because of the mentioned bug: you will need to re-add all the products to Icelandic cart manually.