Address a missed commitment with a team member I don't manage

Help me address a missed commitment with someone on my project team who does not report to me. Their role and who they report to: [DETAILS] What they committed to and when: [TASK and original date] What happened: [missed by how much, any pattern, what they said] Impact on the project: [what slips or who is affected] What I know about their situation: [competing priorities, workload, skills gap, unclear expectations] My relationship with them: [new / good / strained] Help me handle it in this order: 1. Check myself first: was the task clear, was the date agreed or imposed, did they have what they needed? List questions I should honestly answer. 2. The conversation: an opening that is direct but not accusatory, questions to understand the cause, and how to agree a new commitment that is realistic. 3. Common causes and responses: competing priorities from their manager, unclear requirements, skills gap, overload, low buy-in - with what to do for each. 4. When and how to involve their line manager: as a resource-planning conversation, not a complaint - with a short script. 5. Preventing repeats: how to make commitments visible and confirm them in writing without micromanaging. Return: - A conversation plan with suggested wording. - A follow-up note confirming the new commitment. - A message to their manager, if needed, focused on priorities and capacity. Keep the tone respectful and assume good intent until the facts say otherwise.