Accessing site via NGINX via istio ingress

We are using AKS cluster and configured Istio 1.8.
App Gateway is configured/linked with Istio-ingress gateway and all.

When we access application, request goes till Nginx and then throws error “HTTP ERROR 426”.
Expectation is Call from Nginx should go further to nodejs/auth and continue.
Whereas, if I access a static page on Nginx, it loads perfectly fines.

Any thoughts?