This topic applies to LobbyCentral On-Premise customers only.

If LobbyCentral is configured to run with Single Sign-On mode enabled, the web server must be properly configured to ensure that end-users can connect to it.

A requirement for SSO is that Anonymous Access is disabled and Windows Authentication is enabled in IIS.  When Windows Authentication is enabled, the web browser must send the username and password to the server.  

The user that is logged in must be a domain account that is permitted to connect to the web server.

If the browser does not send the required information, or if the user cannot be authenticated, or if the browser is unable to obtain the current user's credentials,  Internet Explorer will display a Windows Security login, prompting the user to enter their windows and password.

This is not a symptom of LobbyCentral, but of the web browser and/or security configuration.

Please see the following Microsoft article regarding Internet Explorer and Windows Authentication