According to the PMP Exam Content Outline, one of the tasks of a project manager in the leading domain is to "Communicate roles, responsibilities, and reporting relationships to team members and stakeholders in order to create a project team environment that fosters performance." This implies that the project manager should reaffirm the required project obligations directly with the team member who failed to communicate the reason for their absence from three team meetings. The project manager should clarify the expectations and consequences of the team member's behavior, and provide constructive feedback and coaching to help them improve their communication skills and accountability. The project manager should also document the issue and the actions taken to resolve it, and monitor the team member's performance and attendance. Reaffirming the project obligations directly with the team member can help to prevent further misunderstandings, conflicts, or delays in the project, and enhance the team member's engagement and commitment. References:
PMP Exam Content Outline
A Guide to the Project Management Body of Knowledge (PMBOK Guide), Sixth Edition, Chapter 9.4.2.1 and
9.4.3.2
Business Analysis for Practitioners: A Practice Guide, Chapter 4.4.1 and 4.4.2 How do project managers deal with unplanned leaves?1 How to deal with a team member who keeps missing deadlines?2

The project manager should plan for incremental and iterative delivery based on feedback from the marketing and sales team because this is an example of adaptive development approach, which is suitable for projects with high uncertainty and changing requirements. By delivering value in increments and iterations, the project manager can validate the assumptions and benefits of the project, and adjust the scope and direction as needed. This way, the project manager can address the stakeholders' concerns and ensure that the project delivers the most efficient and effective sales channels for the organization. References:
* PMBOK Guide, 6th edition, page 18, section 1.2.3.2
* PMI-PBA Guide, 1st edition, page 13, section 1.3.2.2
* PMP Sample Test Questions, question 1
* Free PMP Practice Exam Questions, question 1
* PMP Questions page 484, question 484

According to the Agile methodology, the product owner is the role that manages the product roadmap and prioritizes the backlog1. They also define the product vision and manage stakeholders2. They have the authority to make key decisions and ensure that the team is working on the right items1. The product owner is also responsible for maintaining the conceptual and technical integrity of the work the team is responsible for3. Therefore, the product owner is the best person to understand, develop, and prioritize a list of functionalities for a public service project.

According to the PBA Guide, the project manager should validate the stakeholder's understanding of the project management plan during the kick-off meeting, which is a formal meeting to communicate the start of the project and the expectations of the stakeholders1. This is also consistent with the PMBOK Guide, which states that the project manager should ensure that the project management plan is approved by the appropriate stakeholders and that the approval is based on a common understanding of the project scope, objectives, deliverables, and milestones2. By validating the stakeholder's understanding during the kick-off meeting, the project manager can prevent misunderstandings, conflicts, and delays that may arise later in the project due to different levels of understanding by international stakeholders. References:
* 1: PBA Guide, Chapter 3, Section 3.4.1, Page 63
* 2: PMBOK Guide, Chapter 4, Section 4.2.3.1, Page 89

A stakeholder engagement plan (SEP) documents how involved and influential your project stakeholders are. It also outlines your stakeholder communication plan, including when you'll reach out to each stakeholder, what platform you'll use, and how much information you'll deliver1. The project manager should assess the information requirements of the community to ensure effective communication and engagement.
This involves understanding what information the community needs, how they prefer to receive it, and how often they need updates. This approach helps to build trust, manage expectations, and foster a positive relationship with the community, which can contribute to the success of the project1. References: Asana Resources | Project management | 5 steps to creating a stakeholder engagement plan