Ambassador Host {hostname}: invalid TLS secret ssl-cert, marking inactive

I am using the Ambassador in my GKE cluster. I am getting below issue but I am having valid ssl certificate as secret in my configuration.

Secret myapp-ssl-cert.ambassadorpoc unknown
Host myapp: invalid TLS secret myapp-ssl-cert, marking inactive

My host yaml file looks like below:

apiVersion: getambassador.io/v3alpha1
kind: Host
metadata:
    name: myapp
    namespace: ambassadorpoc
spec:
    hostname: '*'
    selector:
        matchLabels:
            hostname: myapp
    acmeProvider:
        authority: none
    tlsSecret:
        name: myapp-ssl-cert
    requestPolicy:
        insecure:
            action: Redirect
            additionalPort: 8080

Can anyone help me resolve this issue.