Upgrading vCenter Server fails at upgrade pre-check with error "Unsupported NSX version registered with vCenter."

Products

• VMware vCenter Server

Issue/Introduction

• Upgrading vCenter to version 8.x or 9.x fails during the pre-upgrade validation with the error: “Unsupported NSX version registered with vCenter.”
  
  
  
• NSX is not deployed or operational in the environment.
  
  
• The Extension Manager in the vCenter Managed Object Browser (MOB: https://<vcenter-ip-or-fqdn>/mob/?moid=ExtensionManager)  lists the com.vmware.nsx.management.nsxt extension:
  

Environment

VMware vCenter Server 8.x

VMware vCenter Server 9.x

Cause

• The vCenter Server ExtensionManager contains a stale NSX extension registration com.vmware.nsx.management.nsxt.
• Regardless of whether the NSX Manager appliances have been decommissioned or are unused, the upgrade installer checks all registered extensions for compatibility.

Resolution

1. Take a snapshot of the vCenter Server Virtual Machine before proceeding with the changes. For vCenter in Enhanced Linked Mode,
   Refer: VMware vCenter in Enhanced Linked Mode pre-changes snapshot (online or offline) best practice
   
   
2. Since NSX is not in use, manually unregister the extension via the vCenter Managed Object Browser (MOB).
   Refer: Remove NSX Extension from VMware vCenter