Unable to access HTTPS URL with istio gateway setup

Question

unable to access

apiVersion: networking.istio.io/v1beta1
kind: Gateway
metadata:
  name: gateway
  namespace: istio-config
spec:
  selector:
    istio: ingressgateway
  servers:
  - port:
      number: 443
      name: https
      protocol: HTTPS
    hosts:
    - "*.mycorp.us.com"
    tls:
      mode: SIMPLE
      credentialName: mycorp-cert
---

apiVersion: networking.istio.io/v1beta1
kind: VirtualService
metadata:
  name: wf-virtualservice
  namespace: istio-config
spec:
  hosts:
    - "myservicename.mycorp.us.com"
  gateways:
    - gateway
  http:
    - match:
        - uri:
            prefix: /
      route:
        - destination:
            host: myservicename.mycorp.us.com
            port:
              number: 443

I have enabled mTLS with the above manifest files to access the swagger URL of my app using https.

apiVersion: security.istio.io/v1beta1
kind: PeerAuthentication
metadata:
  name: default
spec:
  mtls:
    mode: PERMISSIVE

I get 503 when accessing it. If I disable mTLS, I'm able to access the swagger URL myservicename.mycorp.us.com using HTTP by changing the port in the gateway manifest and replace 443 with 80 where ever applicable, as below

  - port:
      number: 80
      name: http
      protocol: HTTP
    hosts: 
    - "*.mycorp.us.com"

I do have an external LB setup and a static IP setup xx.xxx.x.145

NAME                   TYPE           CLUSTER-IP       EXTERNAL-IP     PORT(S)                                      AGE
istio-ingressgateway   LoadBalancer   xx.xxx.x.145   xx.xxx.x.177   15021:31010/TCP,80:32358/TCP,443:30515/TCP   17d
istiod                 ClusterIP      xx.xxx.235.15    <none>          15010/TCP,15012/TCP,443/TCP,15014/TCP        17d

Unable to figure out what's wrong with my configuration or manifest. Appreciate it if someone helps with this.