Error: There was an error unconfiguring the vSphere HA agent on this host

Products

• VMware vCenter Server
• VMware vSphere ESXi
• VMware vSphere Kubernetes Service

Issue/Introduction

When attempting to configure or re-enable vSphere High Availability (HA) on an ESXi host within a Supervisor cluster, the task fails with a specific configuration error.

Symptoms:

• The vSphere Client displays: HA - There was an error unconfiguring the vSphere HA agent on this host. To solve this problem, reconnect the host to vCenter Server.
• The Fault Domain Manager (FDM) logs (fdm.log) stop recording new entries.
• The Supervisor cluster status for the host remains stuck in a "Configuring" state for an extended period.
• Attempts to reconnect or reconfigure the host do not resolve the issue.

Environment

• VMware vCenter Server 8.0.x
• VMware vSphere ESXi 8.0.x
• VMware vSphere with Tanzu (Supervisor Cluster)

Cause

The vSphere HA agent (FDM) installation is blocked because the host management agents are deadlocked. This deadlock is caused by a hung Spherelet process or a vSphere Kubernetes Service (VKS) task that is stuck in a transient configuration state. While these services are unresponsive, the host cannot process the VIB installation required for HA.

Resolution

To resolve this, the host management services must be cleared via a reboot. Follow these steps:

1. Place the affected ESXi host into Maintenance Mode. Ensure all Virtual Machines are evacuated to other hosts in the cluster.
2. Reboot the ESXi host.
3. After the reboot completes, exit Maintenance Mode.
4. Right-click the host in the vSphere Client and select Reconfigure for vSphere HA.
5. Monitor the Summary tab to verify that the HA agent status is Connected and the Supervisor cluster status returns to Healthy.