External IP returning 502

[subinsabu390]

I have a testing cluster with ambassador 1.9 version in GCP. As per the docs, I have updated the same to ambassador version 1.14 and everything is working fine. But on upgrading from 1.14 to 2.3.2 according to the docs eliminating downtime(running both the versions in parallel), my ingress backends have become unhealthy and external ip is now returning an 502.

I have applied all the resources according to the docs including the listener, host, etc.

ingress.yaml
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
annotations:
kubernetes.io/ingress.global-static-ip-name: testapp-api-ip
networking.gke.io/managed-certificates: api-cert
name: api-services
spec:
defaultBackend:
service:
name: edge-stack
port:
number: 80
status:
loadBalancer:
ingress:
- ip: xx.xxx.xx.xx

Update:
Since upgrading from 1.14 is not working. I have tried a different approach to remove the current ambassador resources and applied a fresh version of ambassador 2.3.4, still it's not working. NEG is unhealthy, health check path is /ambassador/v0/check_ready

Any sort of help is appreciated. Please comment for more details.