This is not likely to be a Laserfiche issue. What browser are they using?

Firefox and Chrome will prompt for credentials, though I think Chrome will try to follow IE settings.

Internet Explorer and Edge only pass the credentials without prompting if the site is considered as internal site (in other words, if the server address does not contain a period in its name - https://WebAccessServer/laserfiche would be considered an internal site, while https://WebAccessServer.Domain/laserfiche would not even though it points to the same server). In Internet Explorer, a URL using the fully qualified server name can be added to trusted sites to make integrated Windows authentication work (and trusted sites can be pushed to all machines through group policies). Edge does not yet support trusted sites.