Do not disable the secure port.
The secure port is used to serve https with authentication and authorization. If you disable it, no https traffic is served and all traffic is served unencrypted.
You need to set the API Server up with the right TLS certificates.
Edit the API server pod specification file '/etc/kubernetes/manifests/kube-apiserver.yaml' on the master node and either remove the '--secure-port' parameter or set it to a different (non-zero) desired port.