Firewall

If a firewall is located between the server and the workstations, it is essential to ensure that the ports required for communication are open in both directions (inbound and outbound).
The following ports must be accessible:

• 22: SSH (remote access and secure transfers)

• 9: Wake-on-LAN

• 5900: VNC (remote control)

• 3389: RDP (Remote Desktop Connection)

• 35621 and 35623: Backups

• 5985 and 5986: WinRM (HTTP/HTTPS remote management)

In summary:
Verify that these ports are not blocked by the server’s firewall, client workstations, or any intermediate network equipment (router, hardware firewall, etc.).