I use a number of external hard drives for Hyper-V. It looks like Hyper-V can get quite confused sometimes if a) the Bitlocker encryption is not unlocked before starting the Hyper-V Manager, or b) the external drive is not attached. Like in this case. “The application encountered an error while attempting to change the state of VMNAME…’ Start failed.
And once you close the message, you can see ‘Cannot connect to virtual machine configuration storage’
I tried to restart the Hyper-V Management Service. No help. I guess the solution for this one is easy, but I don’t have time for this. So I fixed it by creating a new VM and attaching the drives / images to the VM. Sometimes I feel little problems like this are not worth the time to try to fix if you can do it with a new VM in two minutes.