I have a server that no one can reach remotely so I need someone to figure out what is wrong.

I have a Windows Server 2012 R2 domain controller that needs to be configured for Remote Desktop access. Local and remote connections (from Macs in Winnipeg and from Ontario) are failing. The job is to diagnose and fix the RDP issue (error code 0x204), verify proper network adapter and IP configuration, confirm firewall and group policy settings, and ensure secure remote access is working. The environment uses a Hitron router with port forwarding set up.