Cluster image cannot be extracted from the SDDC Manager UI as the dropdown is grayed out.
In the domainmanager.log the following exception can be seen:
VMware Cloud Foundation 4.x
VMware Cloud Foundation 4.5
When a cluster in VCF is in "ERROR" state and a vSphere cluster was not created in the vCenter for that cluster.
This issue is resolved in VMware Cloud Foundation 4.5.1.
Workaround:
Deleting the cluster directly from the SDDC Manager, either via the UI or the API.
To delete a cluster, Refer - "Delete a vSphere Cluster from a Workload Domain"