I've been trying to get that invoice for the past hour and I've been on call with the support staff. The staff is not used to European financial laws, and it's hard to explain what an invoice is. As of right now, the above link works for me, I see the order, but when I try to open it, It just says "Ooops, something went wrong, contact support".
Not at all the support staff's fault, but Apple's. A PDF business to business invoice is not that hard to implement tbh.