Cert-Manager (no matches for kind "Issuer" in version "certmanager.k8s.io/v1alpha1)

You missed the step in the docs:

The part

# Install the CustomResourceDefinition resources separately
kubectl apply --validate=false -f https://github.com/jetstack/cert-manager/releases/download/v1.0.4/cert-manager.crds.yaml

Best Regards,
ArgonQQ