gRPC Asp Net Core 3.1 APIs don't work when running on Kubernetes

Question

Following my previous question, I've set my Asp Net Core 3.1 app to only use HTTP2 protocol. Actually it solved my issue, at least locally.

But when I deploy the server app on Kubernetes, my client app (a net core 3.1 demo console app), throws an exception:

upstream connect error or disconnect/reset before headers. reset reason: connection termination

I did some research online and it seems to be related to the Kubernetes configuration. Since this is the first time I use Kubernetes, I don't exactly which part is wrong and why.

My deployment script is:

apiVersion: apps/v1
kind: Deployment
metadata:
    name: ***-service-beta
    namespace: ***-staging
spec:
    selector:
        matchLabels:
            app: ***-beta
    template:
        metadata:
            labels:
                app: ***-service-beta
        spec:
            containers:
                - name: ***-service-beta
                  image: __image_name__
                  imagePullPolicy: Always
                  ports:
                      - containerPort: 16050
                  resources:
                      limits:
                          cpu: 500m
                          memory: 2Gi
                  env:
                      - name: ***
                        value: ***
                      - name: ***
                        value: ***
---
apiVersion: v1
kind: Service
metadata:
    namespace: ***-staging
    name: ***-service-beta
spec:
    selector:
        app: ***-service-beta
    ports:
        - protocol: TCP
          port: 16050
          targetPort: 16050
---
apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
    namespace: ***-staging
    name: ***-service-beta
    annotations:
        kubernetes.io/ingress.class: istio
spec:
    rules:
        - host: ***-service-beta.***.k8s.***.***
          http:
              paths:
                  - backend:
                        serviceName: ***-service-beta
                        servicePort: 16050

My client code. Not sure if I need to set the port?

static async Task Main(string[] args)
{
    AppContext.SetSwitch("System.Net.Http.SocketsHttpHandler.Http2UnencryptedSupport", true);

    using var channel = GrpcChannel.ForAddress("http://***-service-beta.***.k8s.***.***");
    var client = new EventService.EventServiceClient(channel);
    var reply1 = await client.GetTrackEventAsync(new GetTrackEventRequest { Name = "01Austra14" });
}

The server provides both REST and gRPC APIs on the same port. RESTful APIs are working.

I would be glad if anyone can help me