Expired subscribers, as the name implies, have passed their account's expiration date.
View expired subscribers on the People >> Subscribers >> Expired page of the Omnilert admin portal. Expired and/or unvalidated subscribers are hidden from other lists of subscribers.
A subscriber will appear on this list automatically if their account's expiration date is before the current calendar date.
To "un-expire" an expired subscriber account, simply edit their account and set a new expiration date that is later than today's date or set them to "Never expire."
Note: A subscriber's initial expiration date is set when the subscriber account is created according to the Settings >> System >> Expirations settings.