It is not possible to access chat sessions considered "incomplete" (when only one user took part in the conversation, according to our tests) when there are "complete" ones.
The "List all sessions" link is therefore not visible in this case.
In order to display all chat sessions (complete or incomplete), once on the chat page, click on the "Consult previous sessions" link then add "&show_all=1" to the url.
It would be very interesting to have access to the link displaying all the old chat sessions, in any context.
Thanks in advance.