When Trying to start hyper-V VM you get General access denied error (0x80070005)

If you get error “General access denied error (0x80070005)” when starting VM from cluster manager in Hyper-V that means the disk lost its security permissions . in order to get them back 

Detach the VHDx with the “remove” remove button in Hyper-v or 
Failover cluster manager. Just make sure you don’t remove the actual file!

Attach the VHDx again.
Now you can start the VM.

You can also try to give the VHDX file its right permission back  :

1. In this example is the virtual machine ID 684B169F-DB4A-493F-B34A-762E205AB1E4

2. Go to the node wich host this VM Open an elevated command prompt
   
   icacls <path of vhd> /grant "NT VIRTUAL MACHINE\<Virtual machine ID>":(F)

3. Start the virtual machine

Good Luck