The following warning appears on and ESXi host summary page (Issue and Alarms) in vSphere Client:
Your host license expires in XX days. The host will disconnect from vCenter Server when its license expires.
VMware vCenter Server
VMware vSphere ESXi
vpxa monitors license expiry periodically and post this event as issue when approaching license expiring date(default within 15 days).
Apply a valid license to ESXi host. For more information, see Managing licenses on ESXi hosts using the vSphere Client.
For information on the impacts resulting from the expiration of an ESXi host or vCenter Server license, see Impact of vCenter/ESXi license expiration.