I recently ran into a problem when deploying new machines either from a template or a “empty” machine
Error 801 Ensure the library object is valid and then try the operation again , looking at the library server there was access I could open the files no errors at all.
Bing Search to the rescue
When performing any operation on a virtual machine (VM) in System Center 2012 Virtual Machine Manager (VMM), the job fails with the following error:
VMM cannot find the Virtual hard disk object’ error 801
That sounds like a spot on match
Backup VMM Database
Stop VMM Services
Run SQL Script
And we back in action.
Not quite sure what caused the issue will try to look if I see it again.