NLB Target Group stickiness is always set to Off even we enabled the sticky in the K8s yaml

We enabled the stickiness for NLB in the K8s yaml using annotation below, but when we check the target group, it always showing Stickiness is off. Do you know what is the reason? service.beta.kubernetes.io/aws-load-balancer-type: "external" service.beta.kubernetes.io/aws-load-balancer-name: fcubs-gateway service.beta.kubernetes.io/aws-load-balancer-nlb-target-type: instance service.beta.kubernetes.io/aws-load-balancer-target-group-attributes: stickiness.enabled=true,stickiness.type=source_ip service.beta.kubernetes.io/aws-load-balancer-target-group-attributes: proxy_protocol_v2.enabled=true service.beta.kubernetes.io/aws-load-balancer-attributes: load_balancing.cross_zone.enabled=true