When upgrading a 4.11.33 cluster to 4.12.21, the Cluster Version Operator is stuck waiting for the Network Operator to update:

$ omc get clusterversion
NAME      VERSION   AVAILABLE   PROGRESSING   SINCE   STATUS
version   4.11.43   True        True          14m     Working towards 4.12.21: 672 of 831 done (80% complete), waiting on network

CVO pod log states:

2023-06-16T12:07:22.596127142Z I0616 12:07:22.596023       1 metrics.go:490] ClusterOperator network is not setting the 'operator' version

Indeed the NO version is empty:

$ omc get co network -o json|jq '.status.versions'
null

However, it's status is available and not progressing, not degraded: 

$ omc get co network
NAME      VERSION   AVAILABLE   PROGRESSING   DEGRADED   SINCE
network             True        False         False      19m
   
Network operator pod log states:

2023-06-16T12:08:56.542287546Z I0616 12:08:56.542271       1 connectivity_check_controller.go:138] ConnectivityCheckController is waiting for transition to desired version (4.12.21) to be completed.
2023-06-16T12:04:40.584407589Z I0616 12:04:40.584349       1 ovn_kubernetes.go:1437] OVN-Kubernetes master and node already at release version 4.12.21; no changes required

The Network Operator pod, however, has the version correctly:
$ omc get pods -n openshift-network-operator -o jsonpath='{.items[].spec.containers[0].env[?(@.name=="RELEASE_VERSION")]}'|jq
{
  "name": "RELEASE_VERSION",
  "value": "4.12.21"
}

Restarts of the related pods had no effect.  I have trace logs of the Network Operator available.  It looked like it might be related to https://github.com/openshift/cluster-network-operator/pull/1818 but that looks to be code introduced in 4.14.

I have not reproduced.

1.  Cluster version began at stable 4.10.56
2.  Upgraded to 4.11.43 successfully
3.  Upgraded to 4.12.21 and is stuck. 

CVO Stuck waiting on NO to complete, NO 

NO to update its version so the CVO can continue.

Bare Metal IPI cluster with OVN Networking.