When you see that a backup is running in Saved State, I kind of have a "standard" checklist to see if the VM matches the requirements for online backup. You can check these:
1. Is the child VM must in the running state. (I am sure it is yes but this is part of my standard research )
2. Is the Snapshot File Location for the VM set to be the same volume in the host operating system as the VHD files for the VM?
3. Are all volumes in the child VM basic disks and are there no dynamic disks?
4. Are all disks in the child VM use a file system that supports snapshots (for example, NTFS, ReFS)?
5. The latest Integration Services must be installed and backup (volume snapshot) within those services must be running
6. The guest OS inside the VM must support VSS
7. Following services must be running in the VM: COM+ Event System/ Distributed Transaction Coordinator/ Remote Procedure Call (RPC)/ System Event Notification/ Volume Shadow Copy. (Some are set to start automatically, others automatically (Delayed start). The COM+ System Application/ Microsoft Software Shadow Copy Provider services must at least be set to Manual
8. Check inside the guest for event ID 13 with source vmicvss. If that exists, something is wrong