After you run flutter build web, make sure to check the build/web/assets/ folder to confirm that all your assets were actually included in the build.

Also, watch out for the base href in your index.html.

If you’re deploying your app to a subdirectory like https://example.com/myapp/ but your index.html still has <base href="/">, your app might not get loaded correctly. You’ll need to update it to something like <base href="/myapp/"> so the browser can find all the resources in the right place.