The rejected status is displayed in the participants' list in the organizer's tool when an organizer rejected a participant's attendance to the event.
The organizer is able to revoke the rejection by clicking on Edit and Revoke rejection.
The canceled status appears when a participant canceled his participation in your event. In order to revoke the cancellation, the participant needs to log in to his b2match account and update his attendance to the event by selecting at least an event session. The organizer is unable to revoke the participant's cancellation.
Participants who canceled their participation are still visible on the participants' list on the website. If the organizer wants to remove them from the list, they need to deactivate their visibility by clicking on the green eye in the participants' list in the organizer's tool.