Diagnose missing alerts

1. Confirm the check changed health and has the intended incident or recovery.
2. Confirm the correct notification group is assigned to the check.
3. Confirm that group contains a delivery channel or eligible member/roster.
4. For users, inspect assignment schedules and personal delivery preferences.
5. Inspect Notification history for actual attempts and errors.
6. Test corrections with a controlled nonproduction incident.

Delivery path	Common cause
Email channel	Invalid/wrong mailbox or recipient filtering
Personal email	Preference disabled or user not on schedule
SMS / voice	Missing E.164 number, preference disabled or delivery failure
Slack	Wrong workspace, bot absent from private channel or authorization failure
Webhook	Private target, network error or non-success response

An incident is not an external delivery receipt. A schedule mismatch can mean no user attempt occurs at all. A queued/failed attempt needs delivery diagnosis, not a different quorum.

Keep an always-available channel if user schedules would leave gaps. The product does not promise automatic escalation or delayed replay at the start of the next shift.