We taught a five-day class this week. On four of the days (M, Tu, W, and F) we were told that they only had the option to chat with the organizer (there was no option to chat with everyone) and they couldn't see a list of other attendees.
But on Thursday, they could chat with all and saw a list.
On some days, my coworker started the session, but on Thursday I started the session. We use the same login and password to start the session. Why would the end user have a different interface based on who started the session?
The GoToTraining settings that allow Attendees to Chat freely are available while in session, through the Organizer's control panel. The next time you start your training double check that your preferred Chat behavior is selected.