PayPal GIROPAY is automatically cancelling the orders

In Germany there is a payment method called giropay.

Unfortunately, when I integrate them one-to-one according to the PayPal documentation, an error occurs.

The giroypay button is rendered normally. However, after I click on it, it loads briefly, jumps to PayPal, and then logs in the console that the order was canceled. Can anyone explain why this is happening?

<script src="https://www.paypal.com/sdk/js?client-id=<?= $env['paypal_client_id'] ?>&components=buttons,payment-fields,marks,funding-eligibility&enable-funding=giropay&currency=EUR"></script><div id="giropay-btn"></div><script>paypal.Buttons({  fundingSource: paypal.FUNDING.GIROPAY,  style: {    label: "pay",  },  createOrder() {    return fetch("/my-server/create-paypal-order", {      method: "POST",      headers: {"Content-Type": "application/json",      },    })    .then((response) => response.json())    .then((order) => order.id);  },  onCancel(data, actions) {    console.log(`Order Canceled - ID: ${data.orderID}`);  },  onError(err) {    console.error(err);  }}).render("#giropay-btn");</script>

If I leave out the fundingSource: paypal.FUNDING.GIROPAY, in my code, the normal PayPal buttons, among other things, are correctly rendered; the payment then works with giropay.