Springshare has changed the way they calculate patron wait times for chat. From Springshare:
Yes, we did modify the way that wait time was calculated as part of our December 2017 release. Previously, the wait time was only being calculated if a chat was not picked up at all, or once messages were exchanged. That prevented wait times from being calculated for chats where, for example, patrons left before any messages were exchanged. To avoid that, we now calculate wait time based upon when a staff member clicks the Answer button to claim the chat.
This means that we can no longer calculate the actual wait time for chats, since after accepting a chat the staff member must also type a message to the patron. We have asked them to add the ability to see time until a message was sent. They will discuss it with the LibAnswers team and get back to us.