Chat rooms often become inactive, usually when a project ends. You can manage your list of chat rooms by hiding them from the side bar.
To hide a chat room
In the sidebar, open the chat room.
Choose the ellipsis menu located to the right of the chat room name, then choose Hide from side bar.
To restore a hidden chat room
In the side bar, open the ellipsis menu next to CHAT ROOMS.
Choose View all my chat rooms.
Select the chat room.