@InjectionDev I honestly have no idea, but I wouldn't be surprised. Sphere server and Runuo, for example, implement the same features in different ways. I would not be surprised if pol server relies on a packet response that ultima xna is not sending.
Where does it stop in the login process?
My suggestion would be to turn on packet logging in the config, and in razor, log in with both runuo and the xna client, and see where the differences are.