Help with ingress gateway

We are using Istio 1.8.1 and we are trying to connect our load balancer to ingress gateway nodeport service on port 8443. I added the secret istio-ingressgateway-certs to the istio namespace so that istio can use the certificates to expose ingress gateway service on port 8443. The istio ingress gateway is up and running and we can connect to it using port 8080 but it is failing to connect to secure port 8443. Please advice.