It was all working fine in OpenShift 4.2.0 and 4.2.2, but when I upgraded to OpenShift 4.2.4, the router stopped listening on ports 80 and 443, I could see the pod running with "crictl ps", but a "netstat -tpln" didn't show anything listening.
I tried updating the version back from 4.2.4 to 4.2.2, but I accidentally used 4.1.22 image digest value, so I quickly reverted back to 4.2.4 once I saw the apiservers coming up as 4.1.22. I then noticed that there was a 4.2.7 release on the candidate-4.2 channel, so I switched to that, and ingress started working properly again.
The upgrade page
specifically says "Reverting your cluster to a previous version, or a rollback, is not supported. Only upgrading to a newer version is supported." so is it an expectation for a production cluster that you would restore from backup if the cluster isn't usable?