Yeah, read that article and that part works perfectly. But that just adds the license to the pool of licenses but doesn't actually assign it to the vCenter server. I can see the license but haven't been able to associate it with vCenter. The usage counter remains 0 for that license. As mentioned above, I tried assigning the license to the vCenter instance referenced by its UUID:
$vCenterLicenseAssignmentManager.UpdateAssignedLicense($vCenterUuid, $vCenterLicenseKey, $vCenterDisplayName)
But that did not work as the UpdateAssignedLicense method has been removed from the License Assignment Manager. So I tried exploring the bulk assignment route but am stuck on the TypeID which I cannot find a reference for as to what the valid TypeIDs are. The only example that I have been able to find references a license for vSphere servers.