You have not provided much information about the installation and how the users are supposed to login to the system. Using a webclient with credential type as Windows means that you can only log on to the system if you are on the domain, and have a domain-user-account.
(In most cases that is not the case, and that is why i always says NAVuserPassword and a Certificate (+ it works from “home”/outside the domain).
But again , you did not provide much information to start with about your setup.