Unable to connect to terminal users

Hello, 

So for a bit of background, I have a terminal server architecture, I am able to log into teamviewer on my virtual terminal server succesfully, but whenever I ask a user for their ID to try to connect, it fails to connect. The user is on the same virtual server and terminal server that I have been succesful in connecting to, it's only when I try to connect via teamviewer into the user's remote desktop (on said terminal server) that teamviewer fails to connect. 

Why is it failing to connect?