Are you sure? You should see an “Access Denied” error if the upload fails. I thinks it’s a problem with a policy or CORS configuration. According to your screenshot the bucket permissions seem correct (both checkboxes under the “Manage public access control lists (ACLs)” are unchecked) and you “failed to load resource” looks like the browser simply isn’t allowed to load the image.
I’ve updated the instructions in Set up file and image uploads to S3. Maybe it helps you find the difference in your S3 bucket configuration.