A customer reported that they were receiving error messages when trying to connect to Atlas using SSL from a Windows 2012r2 client running Mongo shell version 3.4.3. Error message was:

2017-04-18T16:11:02.280-0700 E NETWORK [thread1] SSL peer certificate validation failed: unable to get local issuer certificate

The issue was fixed by manually adding the DigiCert intermediate certificate to their shell. As the problem was related to the certificate we use for Atlas it seems that the cert should already be loaded in the mongo shell. It appears that this may be a packaging problem for the Windows build of 3.4.3.