We have several location all over US, and all connected using route base tunneling (VPN). That being said, we recently merge with another company and we sent them a firewall with the same model, brand, and config. All traffic on the firewall are running on the default connection.
Workstation config Troubleshooting:
Remote connection is enable.
RDP port is open
Windows firewall is disabled.
netstat -an. I see the TCP port 3389 is listening.