AWS Ingress-nginx loadbalancer: Targets are not within enabled Availability Zones

Question

I have an EKS cluster with the following set up

2 VPCS 1 prod, 1 stage

each vpc has 3 subnets 1 public and 2 private

each vpc has 1 internet gateway and 1 nat gateway

The private subnets are connected to the natgateway via route table association.

I have an eks cluster and an aws managed nodegroup

the nodegroup is mapped to the private subnets.

I installed an ingress-nginx controller that creates a network loadbalancer.

This network loadbalancer works perfectly in stage, but not in prod.

The network loadbalancers for both vpcs are create in the eu-north-1a zone

The target instance for the staging loadbalancer is created in the eu-north-1a zone while that of the prod loadbalancer is created in the eu-north-1b zone, and returns the following error:

Targets are not within enabled Availability Zones

Some targets are not receiving traffic because they are in Zones that are not enabled for your load balancer.

Unused target zones

eu-north-1b

To resolve

There are two options:

Enable these Zones on the load balancer by visiting the load balancer detail page and adding subnets in these Zones. View load balancer 

Or, deregister targets that are in these Zones. View targets in unused Zones
``` 

So the staging and prod clusters are identical. The subnets and ingress-nginx configs are identical, everything is identical. But I can't seem to figure out why prod is failing, and staging is not. What could I be missing?

The values file for the ingress:

ingress-nginx:
  controller:
    replicaCount: 2
    resources:
      limits:
        memory: 300Mi
      requests:
        memory: 256Mi
    service:
      annotations:
        service.beta.kubernetes.io/aws-load-balancer-type: nlb
      externalTrafficPolicy: Local
      healthCheckNodePort: 30254
    stats:
      enabled: true
    config:
      client-max-body-size: "25m"
      http-redirect-code: "301"
      proxy-buffer-size: 128k
      proxy-buffers: 4 256k
      proxy-connect-timeout: "600"
      proxy-read-timeout: "600"
      ssl-ciphers: "ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384:DHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256:ECDHE-ECDSA-AES128-SHA:ECDHE-RSA-AES128-SHA:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA384:ECDHE-ECDSA-AES256-SHA:ECDHE-RSA-AES256-SHA:DHE-RSA-AES128-SHA256:DHE-RSA-AES256-SHA256:AES128-GCM-SHA256:AES256-GCM-SHA384:AES128-SHA256:AES256-SHA256:AES128-SHA:AES256-SHA:DES-CBC3-SHA"
      ssl-protocols: "TLSv1.2 TLSv1.3"
      # use-forwarded-headers: "true"
      # use-proxy-protocol: "true"
      # compute-full-forwarded-for: "true"
      # enable-real-ip: "true"
      # forwarded-for-header: X-Forwarded-For
      log-format-upstream: '$remote_addr - $remote_user [$time_local] "$request" $status $body_bytes_sent "$http_referer" "$http_user_agent" "$http_x_forwarded_for" $upstream_http_resonseHeaderName $ssl_protocol $ssl_cipher'

  rbac:
    create: true

  serviceAccount:
    create: true