The affected VMs were managed by vCloud and could not be added to a vSAN Snapshot Appliance Protection Group.
The following error was noted:
It was found that once the affected VMs were cloned, the cloned VMs could be added to a vSAN Snapshot Appliance Protection Group.
VMware Snapshot Service Appliance
VMware Live Recovery 9.x
vSAN 8.x
The affected VMs had duplicate VM BIOS UUIDs and only one was permitted to be added to the Snapservice DB.
Following the workaround in KB 2002506 to remove the bios UUIDs from the .vmx files resolved the issue.