Backgound image disapear

Hello everyone.
I have a problem.
when I put images on the backgroud of the page (repeat) everything goes well. I export, record, exit the app.
later when I re-enter the blocs, the background image disappears and gives an error on the console:
[Error] Failed to load resource: the server responded with a status of 404 (Not Found) (fundo-2-1.jpg, line 0)
Captura de ecrã 2020-11-21, às 22.19.56

if I manual edit the file style.css (out of blocs) with correct directory it works

It seems you are linked to a “Hosted Asset” in the Assets Manager, as per your mention of a 404 error. I just tested a hosted background image in a new Blocs 4.0.1 document, but even after changing the filename on my web server, I still have no problem seeing the image after relaunching Blocs, which indicates to me that Blocs 4 is caching the server’s image file (otherwise the filename change would have broken the link).

The fact you needed to edit style.css is interesting. I can only assume the URL to the hosted asset must have changed after you added it in Blocs? If so, I would suggest removing the hosted asset and then adding it back via Asset Manager.