Serverless Service shows "IngressNotConfigured" error

Issue

• When trying to create a Serverless Service as per the example in the documentation, this fails and the following error is shown:

  apiVersion: serving.knative.dev/v1
  kind: Service
  metadata:
    name: sample
    namespace: my-example-namespace
  spec:
  [..]
  status:
    address:
      url: http://sample.my-example-namespace.svc.cluster.local
    conditions:
    - lastTransitionTime: "2021-11-08T09:56:05Z"
      status: "True"
      type: ConfigurationsReady
    - lastTransitionTime: "2021-11-08T09:56:05Z"
      message: Ingress has not yet been reconciled.
      reason: IngressNotConfigured
      status: Unknown
      type: Ready
    - lastTransitionTime: "2021-11-08T09:56:05Z"
      message: Ingress has not yet been reconciled.
      reason: IngressNotConfigured
      status: Unknown
      type: RoutesReady
    latestCreatedRevisionName: sample-00001
    latestReadyRevisionName: sample-00001
    observedGeneration: 1
    traffic:
    - latestRevision: true
      percent: 100
      revisionName: sample-00001
    url: http://sample-my-example-namespace.apps.example.com
  

• The activator Pod in the knative-serving namespace is showing a Failed to probe clusterIP error message:

  {"severity":"ERROR","timestamp":"2021-11-12T12:43:33.191896044Z","logger":"activator","caller":"net/revision_backends.go:357","message":"Failed to probe clusterIP 172.30.122.162:80","knative.dev/controller":"activator","knative.dev/pod":"activator-557d4799f7-qtzfn","knative.dev/key":"example/hello-00001","error":"error roundtripping http://172.30.122.162:80/healthz: context deadline exceeded","stacktrace":"knative.dev/serving/pkg/activator/net.(*revisionWatcher).checkDests\n\t/opt/app-root/src/go/src/knative.dev/serving/pkg/activator/net/revision_backends.go:357\nknative.dev/serving/pkg/activator/net.(*revisionWatcher).run\n\t/opt/app-root/src/go/src/knative.dev/serving/pkg/activator/net/revision_backends.go:402"}