Assigning license to an ESXi host fails with error: "A specified parameter was not correct: licenseKey"

Products

• VMware vSphere ESXi

Issue/Introduction

• Applying license to a host fails with the error:
  
  A specified parameter was not correct: licenseKey.
   
• License can be added to vCenter Server but it is not displayed while adding a host.
• Manually entering the license key while adding the host using Assign a license key displays a message. Some features will become unavailable and the host add fails with the error: A specified parameter was not correct: licenseKey.

Environment

VMware vSphere ESXi 5.1

Cause

This issue usually occurs when the assigned license is higher than the license supported for the host.\

For example, assigning a VMware vSphere 5.5 Enterprise Plus license to a host running ESXi 5.1 results in failure of adding the host to the vCenter Server.

Resolution

Perform a restricted downgrade of the license. An ESXi 5.1 host can be assigned with a higher license by downgrading the license.

Additional Information

You can reuse the vSphere 5.5 license after you upgrade the host to ESXi 5.5.