The Smartcrypt client requires a verified SSL connection to the Smartcrypt Manager. Apple OS X (10.11) and Mac OS (10.12) also require an Application Transport Security (ATS) valid connection. Apple ATS requires a TLS 1.2 connection and also requires a better than SHA1 hashing algorithm on the SSL certificate.
You can test your connection on OS X in terminal with the following (replacing "pkwareops.domain.com/mds" with your URL):
The output you are looking is: