If you have changed the listening port on the Remote Desktop or Terminal Services from its’ default port 3389, then you will also need to configure your client to connect to the new port. Changing the connection port on the RDP clients is quite easy.
To Alter the Port on the client side:
STEP 1. Use Windows search to open Remote Desktop Connection
STEP 2. In the Remote Desktop Conenction window, in the Computer box, scroll to the computer name or IP to which you wish to connect and add a “:Port” (without the quotes) where “Port” is the decimal value of the destination port
STEP 3. Press Connect