After you enrolled for a certification/learning path if the admin has made any changes to the course structure (i.e., added new courses or removed existing courses), the changes will be published as a new version and the old version will no longer be available. In this case, admins would transfer the users from the old version to the new. This is when you will receive a notification about you being moved to the new version.
If you have received this notification, please review your progress for all courses in the learning path/certification and ensure to complete all courses marked as Mandatory in order to complete the overall learning path/certification.