You can directly connect to a slave node in the cluster to verify that the cluster is working correctly. But, you can't just point the browser at the slave's hostname. A Windchill cluster will re-direct client requests back to the cluster alias. What you need to do is temporarily map the cluster alias to the slave node's IP address. The easiest way to do this is to just edit the hosts file on your client machine.
After mapping the cluster alias to one of your slave nodes, open up a browser and connect to Windchill using the cluster alias. This will bypass the load balancer and connect you directly to the slave node. Make sure you can log in and use the Windchill UI. If so, then re-map the cluster alias to the other slave node and test that one as well. If you can use Windchill normally from both slave nodes, then the issue must be with the load balancer configuration.