Please make sure that you have correctly entered your credit card details in your personal settings (Cockpit). You can check this as follows:

Manage subscription - Means of payment (change from invoice to the desired credit card).

Important: Invoices that have already been sent cannot be paid retroactively by credit card. In this case, any outstanding invoices must be paid by bank transfer. You will find the necessary payment information at the end of each invoice. 

You can view and download your invoices including the QR code in your personal settings.