Error: "Licenses could not be assigned to vCenters", seen during license assignment on VCF 9.1

Products

• VCF Operations
• VMware vCenter Server
• VMware Cloud Foundation

Issue/Introduction

• License assignment to a selected vCenter in VCF Operations 9.1 fails with an error message "failed assignments" and "Licenses could not be assigned to the selected vCenter".
  
  
  
  
• Selecting the View Details tab for the error message shows the message below:
  
  This license could not be assigned to the selected vCenter system. Check the network connection between the license server and the selected vCenter system and try again.

Environment

• VCF 9.1
• VVF 9.1

Cause

This issue can occur due to network connectivity problems between the license server and vCenter or VCF Operations. It may also arise if the NTP (time synchronization) configuration on the VCF Operations appliance is missing or incorrect. Such a time drift between vCenter and VCF Operations can cause token requests to expire prematurely, preventing the system from licensing the vCenter and ESXi hosts

• Checking the connectivity from vCenter to license server

If a license has already been assigned to the vCenter and the vCenter becomes disconnected from the license server, vCenter shows a banner indicating that the connection has been lost.

• Checking the connectivity from VCF Operations to the vCenter

From VCF Operations, go to Operate > Inventory > select the vCenter to assign a license to and then select the “Alerts” tab. If there is a connectivity issue from VCF Operations to the vCenter, it shows the alert “Connectivity to the vCenter is affected”.

• Checking the connectivity from license server to VCF Operations

From VCF Operations, go to Manage > Licensing > Licenses & Registration and under Registration and License Server Status select the Manage dropdown > License Servers. Check the column “Connectivity to VCF Operations”. Above mentioned error message is shown if any of these are “Not Connected”. 


NOTE:  Connectivity to the license server can show as connected in this UI if the Licensing Server vAPP was deployed with a valid IP but has invalid DNS records.

Resolution

To resolve this issue, ensure that the time is properly synchronized between vCenter and VCF Operations, ideally using the same NTP server for both. Also, verify that there is proper network connectivity between VCF Operations, vCenter, and the License Server

1. vCenter must be able to connect to the license server.
2. License server must be able to connect to VCF Operations.
3. VCF Operations must be able to connect to the vCenter.

Additional Information

Connectivity diagram between License Server and other components:

• To verify and update the NTP configuration on the vCenter appliance use below document:
  Configure Network Time Protocol (NTP) on the Vcenter
• To verify and update the NTP configuration on the VCF Operations appliance use below document:
  Reconfigure NTP on the VCF Operations Cluster Nodes for Site Protection and Disaster Recovery for VMware Cloud Foundation
• Make sure the Time zone on the vcenter server management UI is also same as that on the NTP server. 

         After updating NTP, allow 5-10 minutes for the vCenter to appear under License Management.