If your server for receiving notifications does not accept one or more messages for more than five days then the webhook will be deactivated. Even if a single message is not accepted, that single message will be retried for 5 days and then the IPN will be deactivated, even though other messages have been accepted.
The notifications that were queuing up for the last five days will be deleted by the deactivation. You still can get these contents by using the other reporting tools of the platform.
The IPNs can be reactivated once you're back up, see configuration section.