Using a PC, had this issue 3 days ago but once I updated minecraft in the Microsoft store. It fixed the download.
It happens on all of my worlds even newly created worlds, like it will download but then when it is about to import the "download failed" comes out. It doesn't save the download also
This happened to me yesterday & today. lost 2 fully decked out diamonds swords into my enchanted bows. Lost my fortune 3 diamond pickaxe to 36 cooked steaks.