On Storj, are the files public or private? When you inpsect element/network requests, there should either be a 403 or 404, depending on the URL. If the files are private, something like BunnyCDN can sign the s3 requests making the file public, but you need to add the keys (preferably read only access) to the BunnyCDN config.
Otherwise, if they're public you can try using Cloudfront by AWS, cause there's a always free 1TB traffic option.
Can you post a screenshot of your config, hiding the keys here? Or if you're not comfortable posting here, feel free to send me a PM.