Host Disconnected from vcenter server

Issue: Host Disconnected from the vCenter server and you might have already referred the following

kb.vmware.com/kb/1003409

What solved it : Check for any VM whether it has snapshots in that host and if it has snapshots.

If removing that VM from the host's inventory is letting the host stay connected in the vCenter server then the VM is the cause.

If VMs in that host has snapshots then connect directly to the host using a vSphere client and consolidate them through the GUI or CLI.

If the snapshot consolidation takes a long time and you don’t want the host to be in a disconnected state till then you can remove the VM from the inventory and bring the host back on and consolidate the snapshots of the VM from a different host through GUI or CLI.

The above can also be used if the vCenter server service is not starting and you have already tried the following.
kb.vmware.com/kb/1007669
kb.vmware.com/kb/1003926
connect directly to all the hosts in that cluster and consolidate all the snapshots and try restarting the vcenter server. It has worked on 2 incidents on a customer site.