Offer a digital product at Klarna?

Question

We are currently developing a small platform where we offer different price plans. The idea now is that the user simply clicks on a button (e.g. 20 dollars) and is redirected to Klarna to pay. I sent the following post to the endpoint https://api.playground.klarna.com/checkout/v3/orders based on the documentation. But I always get the error message

Sorry, the delivery option you chose cannot be processed. Please select another delivery option.

But order_lines.type=digital shouldn't have a delivery, should it? What am I doing wrong?

My Post:

{
    "order_id": "f3392f8b-6116-4073-ab96-e330819e2c07",
    "name": "Women's Fashion",
    "purchase_country": "DE",
    "purchase_currency": "EUR",
    "locale": "de",
    "order_amount": 1900,
    "order_tax_amount": 303,
     "billing_address": {
        "organization_name": "string",
        "reference": "string",
        "attention": "string",
        "given_name": "John",
        "family_name": "Doe",
        "email": "john@doe.com",
        "title": "Mr",
        "street_address": "TestStreet 21",
        "street_name": "TestStreet",
        "street_number": "21",
        "postal_code": "66111",
        "city": "HomeCity",
        "country": "DE"
    },
    "order_lines": [
        {
            "type": "digital",
            "name": "Red T-Shirt",
            "quantity": 1,
            "quantity_unit": "pcs",
            "unit_price": 1900,
            "tax_rate":  1900,
            "total_amount": 1900,
            "total_tax_amount": 303
        }
    ],
       "merchant_urls": {
        "terms": "https://www.estore.com/terms.html",
        "cancellation_terms": "https://www.estore.com/terms/cancellation.html",
        "checkout": "https://www.estore.com/checkout.html",
        "confirmation": "https://www.estore.com/confirmation.html",
        "push": "https://www.estore.com/api/push",
        "validation": "https://www.estore.com/api/validation",
        "shipping_option_update": "https://www.estore.com/api/shipment",
        "address_update": "https://www.estore.com/api/address",
        "notification": "https://www.estore.com/api/pending",
        "country_change": "https://www.estore.com/api/country"
    }

}