Cloud saves are horrible.
I am also having this issue.
My world is about 730MB, and it started having this issue 8/4/26
I am running 26.40.
The game thinks that the world is cloud only based on the icon in the world select screen, despite me having this world locally, it forces me to download from cloud and shows an error when I try do so.
I cannot edit or access the world in any way, in the storage screen, I only have the “download from cloud” option which gives the same error as when I try to open the world.
I am still having this issue on windows 11 version 26.40