When you remove VM from ESXi host, vCenter thinks it is orphaned as it is not removed from vCenter.

Make sure there is no process running for the VM on the ESXi host and then remove the VM from Inventory on the vCenter. Then try to add the VM back to inventory from datastore browser.

You can look into this KB article.

VM is not a plugin, it is an entry in the vCenter database and holds until it is unregistered properly.

Have a look into this KB https://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=10037...

Thanks,

MS