Notification subscriptions that are "required" don't subscribe users who have never logged into Archer
The notification subscription was converted from data driven notifications with the Archer 6.9 upgrade. It's configured to require users to subscribe and not let people unsubscribe. It seems that users who have never logged in are not subscribed and the only way to get the notifications to send is to get the user to log in. Then the subscription becomes effective. There are too many users to run a report to see who is not subscribed.
Oh, that is interesting information. I would recommend to post this question to support to get official answer. In my view, that would be somewhat a blind spot. Is it 100% confirmed that users who never logged in still have their email defined? Maybe you are using self-provisioning via SAML?