Troubleshooting Amazon EKS Authentication Error: "You must be logged in to the server (Unauthorized)"

Encountering the "You must be logged in to the server (Unauthorized)" error when connecting to the Amazon EKS API server? This usually happens because the IAM entity configured in kubectl isn't authenticated by Amazon EKS. This guide details solutions for two scenarios: you are the cluster creator or you are not. If you're the cluster creator, verify that the IAM entity configured for the AWS CLI matches the one used to create the cluster and update your kubeconfig file using `aws eks update-kubeconfig`. If not, map your IAM entity to the aws-auth ConfigMap using `eksctl create iamidentitymapping` or by manually editing the ConfigMap. Finally, don't forget to check CloudWatch logs for troubleshooting.