I Had Created Disk level Snapshot of a VM using On-Host Agent and unable to Index it.
My CP2.2 host and Snapshot host are in Same region with different subsriptions , though CP2.2 has contributor acces and provided access to all Subsriptions.
To index, you need to create a disk level snapshot of a filesystem not a VM. Please remember to check the "application consistent" snapshot option. This guarantees a consistent snapshot by flushing the buffer, quiescing the IO, etc. You can then index the snapshot from the filesystem --> snapshots.
Please let us know if that helps.