One of the most common remote desktop issues.
To check for connectivity, try plugging a laptop into the network port from which the user is trying to connect, and then use the Ping or Tracert command to see if it’s connected to the host server or connection broker. Keep in mind that testing remote desktop connectivity this way will only work if you allow ICMP packets through your network firewalls.
If the problematic user is connecting remotely through a virtual private network (VPN) or Terminal Services Gateway, the remote desktop might not be working because of a problem with the user’s machine, the VPN or gateway, or your remote desktop infrastructure. With these types of remote desktop issues, you’ll have to use process of elimination to diagnose the problem. For example, try connecting to the VPN using a properly configured client computer and a reliable user account to see if you can establish remote desktop connectivity.