cert-manager not resolving challenge : Waiting for HTTP-01 challenge propagation: wrong status code '401', expected '200'

I am using GKE for my services and few of my services use ALB in GCP. I use below ingress to create the ALB and it works fine. but when I look at challenge it is failing with error in description and cm-acme-http-solver is also not getting resolved because of that.

I search a lot on google and I did not find people getting this error much. When we deployed service,2 months back this type of error did not pop up and it has been just last 7 days since we the challenge is failing.

There is no such log I find for challenges orders. only the error. Do I need to add any port access that is blocking the ALB in GCP to access GKE note:MY GKE cluster is private.

How I set up ingress:

ingress:
  enabled: true
  annotations:
    kubernetes.io/ingress.class: 'gce'
  hosts:
    - host: myhost.com
      paths:
        - path: /
          pathType: Prefix
  tls:
    - hosts:
        - myhost.com.com
      secretName: customer-secret-tls

So because I was using the ALB and then letsencrypt as self managed certificate in GCP, while its a best practice to use GCP managed certificate for ALB.

Solution that I applied and resolved the issue is:

I created a certificate in GCP Then I annotated that in my ingress as below

ingress.gcp.kubernetes.io/pre-shared-cert

This annotation will attach the GCP managed certificate to my load balancer.