Did you wait for a while? It takes a few minutes to load the entire 428 worlds from the zip file, your computer also should have at least 8gb of RAM also (close browser tabs if you opened too many)
Unfortunately I can’t afford cloud storage. Worlds that you “store” in the game are stored in your browser only. The user account and login is for sharing published worlds with others in the Discover tab only.
I mean like when I sign in and tried to use a world I download they don't work even when I use the discover tab and download a world it still doesn't work can you use Shapes inc and then I can show you what I mean?