The vSphere HA agent on a host is in the Uninitialization Error state. User intervention is required to resolve this situation.
vSphere HA reports that an agent is in the Uninitialization Error state when vCenter Server is unable to unconfigure the agent on the host during the Unconfigure HA task. An agent left in this state can interfere with the operation of the cluster. For example, the agent on the host might elect itself as master host and lock a datastore. Locking a datastore prevents the valid cluster master host from managing the virtual machines with configuration files on that datastore.
This condition usually indicates that vCenter Server lost the connection to the host while the agent was being unconfigured.
Add the host back to vCenter Server (version 5.0 or later). The host can be added as a stand-alone host or added to any cluster.