When you engagement has the "Authentication Required" setting set, the default behaviour for consumers who are not currently logged in, or whose login effort failed, is that they are unable to start a conversation with the designated agent. Instead, they are redirected to the Offline survey.
For more information, please read these related articles:
Engagement Attributes - https://support.liveassistfor365.com/hc/en-us/articles/115001378305-Engagement-Attributes
Authenticated Chats (MS Portals) - https://support.liveassistfor365.com/hc/en-us/articles/115002139609-Authenticated-Chat-in-the-Customer-Portal
Authenticated Chats (Non Portals) - https://support.liveassistfor365.com/hc/en-us/articles/115002924229-Authenticated-Chats-Non-MS-Portals-