If the review is already announced, a message needs to be send to the reviewers containing the new date and a request to reschedule the review activity. When the new delivery date is unknown, mention to the reviewers that the review is cancelled for now and a new announcement or review request will follow as soon as the new delivery date is known.
If the review is not announced yet, check if the delay is already known by the responsible manager(s). If so, update your review planning accordingly.
Posted in: From a Moderator perspective