Istio install does not work on port 80; 443 works

We setup istio and everything was working on our new cluster. We have pointed our production to the new cluster, but now, we get a connection refused on port 80, but port 443 is working ok.

We’re using knative with istio, if that helps. TLS termination is being done on istio. How do we debug and fix this issue?

i typically share this document with users looking to debug istio configuration.