If a user changes or moves a Telehealth appointment, the Telehealth consultation link will no longer be valid, preventing both the provider and patient from accessing the Telehealth conference.
It will show you a message that "The session already finished" even the Telehealth conference hasn't started yet. 
The reason for the invalidation of the Telehealth consultation link is due to the user modifying the appointment schedule to a different time slot or date. Since the original link is no longer applicable, a new Telehealth Appointment must be created to generate a new Coviu link.
How to Schedule and Access Telehealth Appointments Using Coviu?