This is primarily a stakeholder communication and engagement breakdown. The first action is to ensure the communication method is effective for that stakeholder and supports timely approvals. Assessing whether the channels are appropriate and updating them (C) aligns with communications management: selecting the right medium, frequency, format, tools, and escalation path to match stakeholder needs and constraints. If email notifications are unreliable for that stakeholder, the project manager can implement redundancy (tool notifications plus calendar invites, messaging app alerts, dashboard reminders) and confirm receipt for critical approvals. Escalating to IT (A) may help later, but it addresses a potential technical symptom without first fixing the process and ensuring stakeholder accountability. HR training (B) is excessive and unlikely to resolve immediate project governance needs. Replacing the stakeholder (D) is rarely feasible and escalatory; it can damage relationships and typically lies outside the project manager's authority. Strengthening the communication approach reduces missed sign-offs, prevents further cost impacts, and restores predictable decision-making cadence.