There is a content [Not displaying the chat for a certain amount of time] when the chat has ended.
This certain amount of time is, by default, it is set to be a day. (2019/11）
And this can be changed with the setting below.
(1) Click on the setting button on the upper right of the management page.
(2) Click on [Chat]>[Design]>[Menu] on the left side of the screen.
(3) Click on [Menu]>[End] tab.
(4) Click on [Display detailed setting].
(5) Enter a number in the section [Not display for 〇 minutes] in [Display [Not display the chat for a certain amount of time]].
(6) Click on [Update].