Invalid Host Header

The host header indicates which virtual host the web-server should use. You'll need to define a default host, which is used when the host header does not match any configured virtual hosts. Most web-servers reject your http-request if there isn't a host-header.

Here is a great link to the MDN Documentation on the Host-Header for you to check out:

https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Host

Here is a git post with some steps to resolve your host header:

https://github.com/facebook/create-react-app/issues/2271