"A general runtime error occurred. The key provider clusterName not found on Host <host-fqdn>" when trying to attach a vTPM device to the Virtual Machine

Products

• VMware vCenter Server

Issue/Introduction

1. On attempting to attach a vTPM device to a Virtual Machine, the task fails with error "A general runtime error occurred. The key provider clusterName not found on Host <host-fqdn>" when trying to attach a vTPM device to the Virtual Machine"
2. The vCenter server uses a Native Key Provider which is restored from another vCenter server.
3. The VM in question resides on the vCenter server where the Native Key Provider was originally not created. 
4. Attaching the vTPM device to a VM which resides on the vCenter server where the Native Key Provider was originally created completes successfully.
5. The Host where VM is running is part of a cluster, not a standalone host. Reference kb- Cannot add vTPM on virtual machine or enable host encryption on standalone host. "The host does not support Native Key Provider."

Environment

VMware vCenter Server 7.x
VMware vCenter Server 8.x

Cause

The Native key provider is still not in an "Active" state. This is because when the Native Key provider is restored on another vCenter (not the vCenter server where the key provider was originally created), it goes into a " warning" state and usually takes time to finally be in an "Active" state. In between the said time, any attempts to add the vTPM device on the VM fails with the said error.

Resolution

Ensure that the Key Provider status is "Active" and Not "Warning" or "Unknown".