The first thing that the project manager should do is to review the communications management plan, which is the document that describes how the project information will be communicated to the stakeholders. The project manager should check if the stakeholder’s communication requirements, preferences, and expectations are identified and addressed in the plan. If not, the project manager should update the plan accordingly and ensure that the stakeholder receives the appropriate project status reports. The other options are not the best first actions, as they either do not address the root cause of the problem (lack of communication), or they are premature or unnecessary (updating the stakeholder register or the project management plan). References: PMBOK Guide, page 377-378; PMP Sample Test Questions, question 43