What should a product owner do when a new stakeholder is complaining that they are...

The product owner should ensure that the stakeholder has easy access to relevant project data by utilizing the information radiator. An information radiator is a visual display of important project information, such as progress, financials, and key metrics. By giving the stakeholder access to this information, they can get the data they need without disrupting the team's workflow or waiting for specific requests. The scrum master can help facilitate this process by making sure the relevant data is readily available and visible.