When a host is being removed from inventory, it is typically required to first place the host into Maintenance Mode to do so. In some cases, a host may have been physically decommissioned before being removed from the vSphere inventory. This will cause the host to go into a Not Responding state due to missed heartbeats sent by the vCenter. This of course means that the Host cannot be placed into Maintenance Mode. This article shows how to address this type of situation.
VMware vCenter Server
A host was disconnected from the network for any reason before being removed from the vSphere inventory.
The following steps will work in the majority of cases:
If you experience the Disconnection tasks being stuck for a prolonged period of time, please contact Broadcom Support for further assistance with your issue.