A 401 Unauthorized Error indicates that the requested resource is restricted and requires authentication, but the client failed to provide any such authentication. So, Either you need client certificate to access that service or you need to do some changes in Authentication tab. Try providing the authentication details inside Auth. And to add cleint certificate you need to go to preferences and SSL settings and provide the certificate path inside KeyStore and password.
If this doesn't hep .. Try this also - Enable the "Authenticate preemptively" option in Ready! API Preferences > HTTP.
