Changed Block Tracking Not Supported (code 1933)
A Hyper-V backup plan terminates with the following warning: Changed Block Tracking was not applied for some VM's: their versions do not support CBT with the list of virtual machines with failed backups.
The occurrence of this warning means that the listed VM versions are earlier than 6.2. VM backup operations with Changed Block Tracking require the Hyper-V VM to be version 6.2 or later.
Upgrade the VM version.
Bring the VM offline and upgrade the VM version before it can be backed up. You can upgrade the VM Version by using the Hyper-V Manager or the Update-VMVersion cmdlet.
Read the Upgrade virtual machine version in Hyper-V on Windows or Windows Server to learn how to upgrade the required VMs.