The Routing Protocol for Low-Power and Lossy Networks (RPL) has emerged as a key enabler for communication in resource-constrained Internet of Things (IoT) environments. However, as IoT applications become more diverse and complex, new challenges have arisen in the deployment and operation of RPL-based networks. This paper provides a comprehensive review of the emerging challenges faced by the RPL protocol and explores the latest solutions proposed in the literature to address these challenges. The challenges discussed include network scalability, energy efficiency, security, mobility support, and interoperability. This review contributes to a deeper understanding of the evolving landscape of RPL-based IoT networks and provides insights into potential directions for future research.