Best wishes for 2018!
Regarding your problem, can you verify that the parent VM is indeed deleted from the vCenter server?
You can check the name of the parent VM in the summary of the pool, under the tab vCenter Server.
If the parent VM indeed is deleted from the vCenter, Is there a possibility to restore the machine?
Could be Error related to residual issue after vCenter reboot . Re-enable provisioning on the pool and recompose the desktops in error stateto have clear the error.
I've seen this in two scenarios:
1. The snapshot the pool was based on has indeed been deleted.
2. The snapshot or Gold Image has been manually renamed.
In both instances it is easily recoverable by performing a recompose from another snapshot that does exist. If I remember, it will initially error during the recompose wizard, but you can simply skip past it and select whatever gold image you need & snapshot.
On the chance that your gold image has no snapshots, you should just be able to quickly create one via the normal sealing process:
1. Power on gold image
2. From vsphere console in GI: ipconfig /release
3. Shutdown the VM
4. Take a new snapshot
5. Recompose based on new snapshot
... this of course relies on the hope that whoever deleted the original snapshots didn't then power on the gold image and mess a load of things up, which you may not know if you've recently inherited it. If you went down this route, I'd deploy a test pool first and just double-check that everything works as expected.