Sticky sessions on Istio is not working when i have multiple pods

I have application running with two pods, where i have imperva sending traffic to aws alb and aws alb sending traffic to istio ingress gateway where i have VirtualService and destinationrule which had consistentHashLb, but still when i tried refresh page it sending traffic to two pods.

But if i have enabled stickiness it has to send traffic to only one pod ? Did anyone encounter similar issue ?

I have enabled stickiness on AWS ALB too.