I can't replace a world in the realm that I created

Well, I wanted to create a Realm to play with my friends with the world that we already had, but I have tried to replace the real one with the world that we already had created and it always gives me an error. I do not understand the error which is the following: We could not prepare the file of your world to load it. Could you have a full hard drive?

I have plenty of hard drive space, I have also tried replacing different worlds that weighed less or next to nothing and they all get the same message.

I would like you to give me back the coins spent on this realm since I cannot enjoy it as I would like.

Thanks.