I've added a new .hgx file with the following line added to ignore any certificate warnings:
ServicePointManager.ServerCertificateValidationCallback += (sender, certificate, chain, sslPolicyErrors) => true;
I was getting a 'Error getting response stream (Write: The authentication or decryption has failed.): SendFailure' error and mozroots --import --ask-remove wasn't helping. So I decided to just trust the certificate.