You have a number of virtual machines running on your Windows Server 2016, Windows 10 or Windows Server 2008 R2 Hyper-V system. As soon as you try to start another VM in the Hyper-V Manager console or Start-VM virtmachine via PowerShell, a rather cryptic message keeps preventing you from doing so:
[Window Title]
Virtual Machine Connection[Main Instruction]
The application encountered an error while attempting to change the state of ‘virtmachine’.[Content]
‘virtmachine’ failed to change state.The operation cannot be performed while the object is in use.
[Close]
To resolve this, disassociate any other VM from “Physical CD/DVD device” under media before you retry the operation on the failed VM.