Clusters installed with custom service network. different than default 172.30.0.1, is failing to initialize steps, plugin pods, failing in init phase when trying to login to hard coded, in plugin manifest, the internal URL address for kubernetes server.

Default URL for kubernetes service: 

$ oc get svc/kubernetes -n default 
NAME         TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)   AGE
kubernetes   ClusterIP   172.30.0.1   <none>        443/TCP   8h 

Example of Assisted Installer job:

$ oc get svc/kubernetes -n default
NAME         TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)   AGE
kubernetes   ClusterIP   10.128.0.1   <none>        443/TCP   105m 

Probably the best approach is to use internal DNS https://kubernetes.default.svc

Reference:

https://prow.ci.openshift.org/view/gs/test-platform-results/pr-logs/pull/openshift_release/54722/rehearse-54722-periodic-ci-openshift-assisted-test-infra-master-opct-oci-assisted-periodic/1823146446296190976