Unable to Subscribe OpenShift 4.x Cluster

Issue

• After installing an OpenShift 4.3 Cluster it appears on cloud.redhat.com 'unsubscribed'
• We are unable to attach subscription to our OpenShift cluster. When we try to attach subscription via OpenShift Cluster Manager to that cluster and click on this cluster in the Red Hat Customer Portal we are redirected to https://access.redhat.com/management/systems/Cluster-UUID/subscriptions which produces a 404 - not found error.
  • We see available subscriptions on the Customer Portal, but are not able to attach them.