A delivery is "Waiting on a person" (WAITING_HUMAN)

Check the delivery card and its Activity feed. The usual reasons:

• It's at a human step (merge, sign-off, human QA or review). The card says who it's waiting on. Merge the PR, or use Release / Send back. Owners get a reminder (after 1 hour by default) and later the backup is told (8 hours by default); both are set on Settings or per step.
• A sub-task is at "Human merge" but nobody asked you to merge. On a split delivery it is held for the integration review (its thread says "waiting for the integration review") until the other sub-tasks reach their merge step. If one of them is blocked or paused, bring it back (or call it off) and the review starts. When the review passes, every merge step opens at once. If the delivery itself is waiting as "Integration review", read its summary, then Passed or Send back (see Pass or send back a human step).
• The step's role isn't hired (for example a Security review with no Security Engineer, or auto-routed work for a discipline you haven't hired). Hire the role, change the step, or Release it to skip ahead. The handoff note warns that nothing verified that step.
• The engineer went quiet. A step with no activity for 45 minutes is nudged; at 90 minutes it's parked here and the team is told that it went quiet. Look at what landed (PR, files), then Release or Send back.
• The engineer was at capacity too long, or kept failing and asked for help (see Inbox).
• It's waiting on a question. Answer in the thread or the Inbox.