Hi Jim38462,
Welcome to Centrify!
As Apple dropped the maintenance for SystemCACertificate.Keychain, there is actually no need to download it from other Websites, but instead, load those DoD Intermediate Certificates into System KeyChain. You can simply open up the KeyChain Acess > System then drag and drop the DoD Intermediate Certificates into the System KeyChain(Note: As it is system level, it will prompt for admin password to allow the modification).
Please also make sure they are being trusted and try again. Thank you.
Please feel free to contact us if you need any assistance.
Best Regards,
Albert