This issue occurs when the vCenter Server daemon (vpxd) goes down immediately after it comes up on a host due to a rare timing issue. The vCenter Server loses its connection to ESX Agent Manager (EAM) and NSX is unable to query the deployment status of its components on clusters from ESX Agent Manager.
Rebooting NSX Manager or un-registering and re-registering it with vCenter Server does not resolve this issue as the root cause is a connection failure between vCenter Server and EAM.