AWS Cloud9不允许使用静态manifest.json，但允许使用css文件

I am developing a PWA in AWS Cloud9, but it won't allow my manifest.json to be included/referenced in a link tag. It says "VFS Connection is not present" in dev tools as if it can't find the manifest because it is external to the app. I get a 499 error in the console. This is the same message I get if I stop the node http-server and reload the preview page, because it isn't being served up on port 8080. It DOES find the CSS file in a link tag just fine (in the same folder), so is it because it is rel=manifest, or it won't allow a json file to be included for security reasons, or some other reason? Does anyone know why this file isn't working?I am developing a PWA in AWS Cloud9, but it won