It seems like you have done quite a bit already to enable Remote Desktop on your Windows 7 Professional workstation using a non-standard port (3390). Since you have already checked that the port is open and not blocked by your ISP, here are a few additional steps you can take to troubleshoot the issue:
Additional Checks and Troubleshooting Steps:
- Network Configuration:
- Ensure that the network profiles (domain, private, public) are properly configured on the Windows 7 workstation. For Remote Desktop, it's recommended to set the network profile to either private or domain.
- Verify that the IP address and subnet mask are correct on the Windows 7 workstation.
[]Remote Desktop Configuration: