I got him to write it to me in english, and here we go:
The reason why payment with PayByBill doesn’t work is that the amount in the amount parameter and amount in structured order information differs. See error code;

Error code: nordicinvoice.ui.error.total_amount_differs_in_order_details
Error message: total amount calculated from structured order information and amount parameter differs, but should be the same.

For more information about amount parameter and structured order information please see DIBS techsite; http://tech.dibs.dk/integration-meth...win/paybybill/
Do not hesitate to contact me if there are questions.
Can anyone figure this out? Can someone please tell me where I should look? I am thinking that it might have something to do with taxes?