According to the PMBOK Guide1, project communication management includes the processes of planning, managing, and monitoring project communications. The first process, plan communications management, involves determining the information and communication needs of the project stakeholders, such as the sponsor. The project manager should have analyzed the sponsor's communication requirements, such as the type, format, frequency, and level of detail of the information they need, as well as their preferred communication channels and methods. By doing so, the project manager could have designed and implemented a communication system that meets the sponsor's expectations and needs, and avoids any dissatisfaction or complaints. The other options are not the best preventive actions, as they are either reactive or irrelevant. Confirming that the portal is providing adequate information, verifying that the project team is following the communications management plan, and ensuring the sponsor had the necessary skills to use the portal are all actions that could be taken after the situation has occurred, but they do not address the root cause of the problem, which is the lack of alignment between the communication system and the sponsor's requirements. References:
* A Guide to the Project Management Body of Knowledge (PMBOK Guide) - Sixth Edition
* Project Communication Management - Five Steps | PMI
* ProjectManagement.com - Project Communication Management