Generate letsencrypt SSL certificates with istio

I want to use istio for generating letsencrypt SSL certificates. I’m trying to use cert-manager from istio. I created a istio helm release with certmanager enabled. I want to generate a certificate for a domain, but I’m getting “Issuer letsencrypt-staging not ready” everytime. I can’t figure it out what I’m doing wrong. Any ideas or any good resources for doing this? Here is my certificate.yaml:

apiVersion: certmanager.k8s.io/v1alpha1
kind: Certificate
metadata:
name: te1-com
namespace: istio-system
spec:
secretName: te1-com-tls
issuerRef:
name: letsencrypt-staging
kind: ClusterIssuer
commonName: te1.hugintechnologies.com
dnsNames: