DomainMapping to Kubernetes Service stuck in "Uninitialized"

What version of Knative?

1.0

Expected Behavior

DomainMapping with a Kubernetes Service should become ready.

Actual Behavior

I am trying to use a DomainMapping with a regular Kubernetes Service, as described in the Tips in the docs. The custom host is "my-test.biz".

After creation, the DomainMapping remains in Ready state "Unknown" with Reason "Uninitialized".

The DomainMapping does seem to work OK, because I can hit the Kourier ingress gateway with a Host header to "mytest-biz" and get a 200 back from the service, but the status of the DomainMapping never becomes ready. This seems to be caused by the Kourier probe.

The DomainMapping conditions show this status:

Status:
  Address:
    URL:  http://hotcakes-test.biz
  Conditions:
    Last Transition Time:  2022-07-25T18:32:53Z
    Message:               autoTLS is not enabled
    Reason:                TLSNotEnabled
    Status:                True
    Type:                  CertificateProvisioned
    Last Transition Time:  2022-07-25T18:32:53Z
    Status:                True
    Type:                  DomainClaimed
    Last Transition Time:  2022-07-25T18:32:53Z
    Message:               Waiting for load balancer to be ready
    Reason:                Uninitialized
    Status:                Unknown
    Type:                  IngressReady
    Last Transition Time:  2022-07-25T18:32:53Z
    Message:               Waiting for load balancer to be ready
    Reason:                Uninitialized
    Status:                Unknown
    Type:                  Ready
    Last Transition Time:  2022-07-25T18:32:53Z
    Status:                True
    Type:                  ReferenceResolved

Inspecting the logs of the kourier-control pod shows messages of this form:

{"level":"error","ts":"2022-07-27T04:57:55.987+0800","logger":"kourier.status-manager","caller":"status/status.go:399","msg":"Probing of http://mytest-test.biz/ failed, IP: 172.21.129.123:8080, ready: false, error: unexpected status code: want 200, got 404 (depth: 0)","knative.dev/key":"backend/mytest-test.biz","stacktrace":"knative.dev/networking/pkg/status.(*Prober).processWorkItem\n\t/go/pkg/mod/knative.dev/networking@v0.0.0-20201103163404-b9f80f4537af/pkg/status/status.go:399\nknative.dev/networking/pkg/status.(*Prober).Start.func1\n\t/go/pkg/mod/knative.dev/networking@v0.0.0-20201103163404-b9f80f4537af/pkg/status/status.go:289"}
{"level":"error","ts":"2022-07-27T04:57:55.987+0800","logger":"kourier.status-manager","caller":"status/status.go:399","msg":"Probing of http://mytest-test.biz/ failed, IP: 172.21.129.123:8080, ready: false, error: unexpected status code: want 200, got 404 (depth: 0)","knative.dev/key":"backend/mytest-test.biz","stacktrace":"knative.dev/networking/pkg/status.(*Prober).processWorkItem\n\t/go/pkg/mod/knative.dev/networking@v0.0.0-20201103163404-b9f80f4537af/pkg/status/status.go:399\nknative.dev/networking/pkg/status.(*Prober).Start.func1\n\t/go/pkg/mod/knative.dev/networking@v0.0.0-20201103163404-b9f80f4537af/pkg/status/status.go:289"}
{"level":"error","ts":"2022-07-27T04:57:55.988+0800","logger":"kourier.status-manager","caller":"status/status.go:399","msg":"Probing of http://mytest-test.biz/ failed, IP: 172.21.160.89:8080, ready: false, error: unexpected status code: want 200, got 404 (depth: 0)","knative.dev/key":"backend/mytest-test.biz","stacktrace":"knative.dev/networking/pkg/status.(*Prober).processWorkItem\n\t/go/pkg/mod/knative.dev/networking@v0.0.0-20201103163404-b9f80f4537af/pkg/status/status.go:399\nknative.dev/networking/pkg/status.(*Prober).Start.func1\n\t/go/pkg/mod/knative.dev/networking@v0.0.0-20201103163404-b9f80f4537af/pkg/status/status.go:289"}
{"level":"error","ts":"2022-07-27T04:57:55.988+0800","logger":"kourier.status-manager","caller":"status/status.go:399","msg":"Probing of http://mytest-test.biz/ failed, IP: 172.21.160.89:8080, ready: false, error: unexpected status code: want 200, got 404 (depth: 0)","knative.dev/key":"backend/mytest-test.biz","stacktrace":"knative.dev/networking/pkg/status.(*Prober).processWorkItem\n\t/go/pkg/mod/knative.dev/networking@v0.0.0-20201103163404-b9f80f4537af/pkg/status/status.go:399\nknative.dev/networking/pkg/status.(*Prober).Start.func1\n\t/go/pkg/mod/knative.dev/networking@v0.0.0-20201103163404-b9f80f4537af/pkg/status/status.go:289"}

where those IPs are for the two kourier gateways. If I grab a shell into the kourier-control container, I am able to curl those two IPs if I add a Host: mytest.biz header.

The cluster is using Kourier and Istio Service Mesh.

Steps to Reproduce the Problem

Create a normal k8s service.
Create a DomainMapping with a custom hostname. The DomainMapping will be stuck in "Uninitialized."