Occurs if no Storages are selected (recording flag might have been removed accidentally).
In this case, Notification is displayed.
If Storages are not configured, it is not possible to record Cameras.
If click on the notification, storage configuration dialog will open. See "Configuring Server Storages (Admin Only)".
This notification will hide automatically once Storage has a recording flag set up.
Why Event may work incorrectly
Notifications for this type of Event is hidden in system settings. See "Notifications" for more details.