A stakeholder is concerned the project's defined success criteria are not being met. What should the project manager do next?

When a stakeholder expresses concern about success criteria not being met, the project manager's immediate next step should be to review the established project benefits tracking metrics. This allows the project manager to verify if the current measurements accurately reflect the project's progress towards its defined success criteria and whether the benefits are being realized as planned. Documenting ownership for benefits realization is important but is a proactive step, not a reactive one to a current concern. Developing a benefits management plan should have occurred earlier in the project lifecycle. Updating the business case might be necessary later if the review reveals fundamental issues, but it's not the first step.