VM Backup only supports paid editions of VMware ESXi; the Freeware Edition of VMware isn't supported. If you're unsure whether you have a paid or the freeware edition you can check via VMware's Management Object Browser.

1. You'll need to login to the ESXi host itself via a web browser of your choice in order to access the Management Object Browser (MOB).
   
   
2. The link you'll need to use is https://enter-your-ip-here/mob/?moid=ha-license-manager&doPath=licenses
   
   
3. In this screen, you'll now see editionKey, where you'll see either esxiBasic which denotes its the Freeware Edition or else the name of the licensed edition you are currently running:
   
   Freeware ESXi shows esxBasic or esx.hypervisor.cpuPackageCoreLimited
   
   

   
   

   
   
   The paid edition of ESXi shows the name of the licensed edition