Can't download realm map to replace world

I am trying to implement a 1 player sleep system onto my 10 plus me realm. I download the world, do the command block work then replace the world. Well, I can't download the world at all now. The bottom message appears that I have no storage left but on my phone I have unlimited space. The other photo shows I only have 1 single player world so space isn't an issue. I've tried on my tablet which is brand new and has no space taken up and it still won't work. Same messages. Can you help?