I'm using the cert-manager to manage my ssl certificates in my Kubernetes cluster. The cert-manager creates the pods and the challenges, but the challenges are never getting fulfilled. They're always saying:

Waiting for HTTP-01 challenge propagation: failed to perform self check GET request 'http://somedomain/.well-known/acme-challenge/VqlmMCsb019CCFDggs03RyBLZJ0jo53LO...': Get "http://somedomain/.well-known/acme-challenge/VqlmMCsb019CCFDggs03RyBLZJ0jo53LO...": EOF

But when I open the url (http://<somedomain>/.well-known/acme-challenge/VqlmMCsb019CCFDggs03RyBLZJ0jo53LO...), it returns the expected code:

vzCVdTk1q55MQCNH...zVkKYGvBJkRTvDBHQ.YfUcSfIKvWo_MIULP9jvYcgtsGxwfJMLWUGsB5kFKRc

When I do kubectl get certs, it says that the certs are ready:

It looks like Let's Encrypt never calls (or the cert-manager never instructs) these url's to verify.

When I list the challenges kubectl describe challenges, it says:

Name:         crt-secret-hcgcf-269956107-974455061
Namespace:    default
Labels:       <none>
Annotations:  <none>
API Version:  acme.cert-manager.io/v1
Kind:         Challenge
Metadata:
  Creation Timestamp:  2021-07-23T10:47:27Z
  Finalizers:
    finalizer.acme.cert-manager.io
  Generation:  1
  Managed Fields:
    API Version:  acme.cert-manager.io/v1
    Fields Type:  FieldsV1
    fieldsV1:
      f:metadata:
        f:finalizers:
          .:
          v:"finalizer.acme.cert-manager.io":
        f:ownerReferences:
          .:
          k:{"uid":"09e39ad0-cc39-421f-80d2-07c2f82680af"}:
            .:
            f:apiVersion:
            f:blockOwnerDeletion:
            f:controller:
            f:kind:
            f:name:
            f:uid:
      f:spec:
        .:
        f:authorizationURL:
        f:dnsName:
        f:issuerRef:
          .:
          f:group:
          f:kind:
          f:name:
        f:key:
        f:solver:
          .:
          f:http01:
            .:
            f:ingress:
              .:
              f:class:
              f:ingressTemplate:
    UID:                   09e39ad0-cc39-421f-80d2-07c2f82680af
  Resource Version:        19014474
  UID:                     b914ad18-2f5c-45cd-aa34-4ad7a2786536
Spec:
  Authorization URL:  https://acme-v02.api.letsencrypt.org/acme/authz-v3/1547...9301
  Dns Name:           mydomain.something
  Issuer Ref:
    Group:  cert-manager.io
    Kind:   Issuer
    Name:   letsencrypt
  Key:      VqlmMCsb019CCFDggs03RyBLZ...nc767h_g.YfUcSfIKv...GxwfJMLWUGsB5kFKRc
  Solver:
    http01:
      Ingress:
        Class:  nginx
        Ingress Template:
          Metadata:
            Annotations:
              nginx.org/mergeable-ingress-type:  minion
        Service Type:                            ClusterIP
  Token:                                         VqlmMCsb019CC...03RyBLZJ0jo53LOiqnc767h_g
  Type:                                          HTTP-01
  URL:                                           https://acme-v02.api.letsencrypt.org/acme/chall-v3/15...49301/X--4pw
  Wildcard:                                      false
Events:                                          <none>

Any idea how I can solve this issue?

Update 1:

When I run curl http://some-domain.tld/.well-known/acme-challenge/VqlmMCsb019CC...gs03RyBLZJ0jo53LOiqnc767h_g in another pod, it returns:

curl: (52) Empty reply from server

When I do it locally (on my PC), it returns me the expected challenge-response.