After a rewrite of a good portion of the TNTcpLobbyClient file, and compiling the server, I am successfully adding, updating, and removing servers from the lobby server. Looks like I solved the issue.
Might want to make note of this issue for future releases of TNet3:
There are two AddServer and RemoveServer methods in TNTcpLobbyClient, one is an override for the base class of TNLobbyClient, the other is a void method declaration. The overrides were the only methods to actually add and remove a server - but were never called when using TNServerInstance.Start(). The methods being called were the two void methods but the void methods didn't implement the use of mList.Add() or mList.Remove() - so the server's were never added.