This article explains the basics of error handling in APIs in API Connect 2018.

If OpenShift is installed with the ovs-multitenant network plugin then by default pods cannot communicate with pods in other namespaces, with the exception of the default namespace.

With ICP on OpenShift ingress is installed into the kube-system namespace and so if ovs-multitenant is enabled then ingress cannot communicate to pods outside of the kube-system namespace.

In order to allow this communication runt he following command

oc adm pod-network make-projects-global kube-system

update This issue also stopped images being pulled from the local docker registry under certain circumstances