When you Deactivate a Project, a user with project management rights Deactivates the Project for all Project members. This makes the Project inaccessible and it no longer appears in the List of active Projects. No further changes can be made. This may cause error messages during data synchronization if Project members have unsynchronized content stored on a mobile device. Therefore, always ensure that all Project participants have synchronized all mobile data before setting it to inactive.
When you Leave a Project, a participant Leaves an active Project via the menu item Leave Project. It then disappears from the "My projects" List and can no longer be accessed. However, other Project members are not affected and the Project remains active.