Load Balancing is enabled, and one of the servers is completely empty without any users logged in.

Login to to the server works without any problem, the AdminTool doesn't show any problem on the Home tab.

First check if the settings for all servers are completely the same.

Then make sure you are using the latest version of TSplus on all servers, and reboot them.

Check if you are using Dynamic Memory on the machines.

If you are, disable it. This is a common issue that has been reported.