Online vs Offline
By default, agents are not seen as "available" by customers - it is assumed that initially "there is nobody home" as your organization is "after hours" - this means that the chat icon on customer portal or external web page turns from
(online)
to
(offline)
and the customer is not able to start a chat without logging in or registering - because it would be impossible to contact the customer by email later on:
or, in older versions: