This is perhaps one of the most unhelpful, generic error messages I have come across in my years of computing. I’m sure we all have our favourites but this one is up there:
could not initialize.
I encountered this myself after converting an Oracle VirtualBox VDI to a Microsoft Hyper-V VHD and attaching it to a Gen 1 Hyper-V VM.
The good news is that the solution is fairly simple and it involves the command line.
On the computer hosting the Hyper-V VM, open up an administrative command prompt and type the following:
net localgroup administrators service /delete
You may need to reboot the computer after executing that command but after that your Hyper-V VMs should load up.