What does "the training is full" mean?
If you are trying to join a session but received a message stating "The training is full", then the session already has the maximum number of attendees that are allowed. You will not be able to join the session unless one of the attendees who has already joined leaves the session.
This is because each GoToTraining organizer's account has a subscription plan with a maximum number of attendees that they can have per session. Once that maximum is reached, no more attendees can join.
To ask if the session is being recorded or if another session will be scheduled, please contact the organizer (i.e., the person who invited you to the session).