The actual solution to this problem is that we need to expose the Network Load Balancer as an “internet-facing” network load balancer. By default it is exposed as a internal facing NLB.
To achieve this we need to add the following annotation
serviceAnnotations:
service.beta.kubernetes.io/aws-load-balancer-scheme: internet-facing
https://kubernetes-sigs.github.io/aws-load-balancer-controller/v2.5/guide/service/nlb/
We can test its now internet facing by attemtping to curl <address>:27017