From the host you are trying to hit the Shopify API from...can you pull up the Shopify web shop through a browser? It sounds like a connectivity issue from your host getting out to Shopify. Also, this might not be applicable, but is your host client trying to SSL connect using legacy TLS (i.e. - TLS 1.1 or 1.2)? Capturing the packet traffic between your host client and Shopify would likely describe any TLS handshake issues.