I just did the same thing. I did a support ticket asking if I could just have what I purchased transferred to Xbox One or at least a refund where I can get an Xbox One Server.
I found out for Xbox One you need to get the nitrado app from Xbox One store (it's free) and purchase a server through that app.
(I wish it stated that on the website when you buy a server, if it does, I didn't see it)
If I get the resolved somehow I'll post again so you can have some closure to this issue or hopefully at least some help for others that have the same problem.