Changed date of Zoom Event but no notification to registrants

[AndyGoodyear]

We had a Zoom Event originally scheduled for today, that we changed two days ago. We have just been advised that many of those who are registered to the event, tried to join it today, and it would seem that they were not sent a notification of the date change from Zoom, nor a new meeting request.

We had over 400 people registered so this is not ideal. Any ideas why?