This happens when the cluster's agencies are disabled in EAM. This usually follows the use of the vSAN Shutdown Wizard, where the Restart Cluster Wizard is not used to restart the cluster afterwards, which re-enables the EAM agencies as part of the workflow.
Resolution
In scenarios where EAM agencies are not functioning as expected following a vSAN shutdown, the following workaround should be applied.
For all future operations, it is strongly recommended to use the Restart Cluster Wizard after completing the vSAN Shutdown Wizard to ensure proper reinitialization of services.
Prerequisite:
Ensure that all virtual machines (VMs) running on the vSAN cluster are accessible and operating normally before proceeding.
Workaround Steps
Retrieve the Cluster MOID
Open the vSphere Client and navigate to the vSphere cluster.
Check the browser's address bar, where the cluster's MOID (Managed Object ID) will be shown in format of domain-c####. (e.g. domain-c10; do not copy anything after the ":")
Retrieve the Server GUID (especially important when using vCenter Enhanced Linked Mode)
Open the vSphere Client and navigate to the relevant vCenter of affected cluster.
Check the URL in the browser's address bar. The "Server GUID" will be shown in format of Folder:group-d1:########-####-####-####-############. The needed GUID is the 32 hexadecimal-digits string. (Do not copy "Folder:group-d1:" as they are not part of the GUID)
To access the EAM Managed Object Browser (MOB), open a browser and go to:
https://<VCENTER_IP>/eam/mob?vmodl=1
To enable EAM Agencies for the Cluster, click on the link under "Methods" called "enable". A pop-up window will appear.
In the value field, input the following XML, replacing "MOID" with the domain-c#### value and "Server GUID" with the actual server GUID:
The "Enable system VMs" task should now complete successfully.
If vCLS VMs Are Still Not Deployed
Put the cluster into retreat mode, then disable retreat mode to force a refresh of the deployment process, steps are mentioned here: Disable vCLS on a Cluster via Retreat Mode