hubble: Unable to load UI. `Error: getaddrinfo EAI_AGAIN`

When I port-forward the hubble-ui service and try to load the UI in a browser, the following happens:

• the web page remains stuck on the “The application is loading, please wait…” page.
• the logs of the hubble-ui pod show the following message:

{
  "name": "frontend",
  "hostname": "hubble-ui-79b6c7c67-z4bs5",
  "pid": 19,
  "req_id": "101ee530-14a9-4580-868a-66fed7c6fd49",
  "user": "admin@localhost",
  "level": 50,
  "err": {
    "message": "Can't fetch namespaces via k8s api: Error: getaddrinfo EAI_AGAIN $ENTER_AKS_CLUSTER_DOMAIN_NAME",
    "locations": [
      {
        "line": 4,
        "column": 7
      }
    ],
    "path": [
      "viewer",
      "clusters"
    ],
    "extensions": {
      "code": "INTERNAL_SERVER_ERROR"
    }
  },
  "msg": "",
  "time": "2020-03-08T18:09:56.167Z",
  "v": 0
}