A guest that is not answering can still be started. The buttons are on that guest's overview, under hypervisor power. Each one asks you to confirm.
Overview shows hypervisor power once this machine is tied to a host and a VM id. files01 is VM 101 on Lab host. The guest is not answering; the buttons talk to the hypervisor. start, shut down, and force off are here even when the guest is offline.
Press start. The label becomes a confirm. Press it again to send start to the host. This shot stops on the confirm, so the guest is not started. Shut down confirms as an ACPI shutdown. Force off confirms as a hard power cut.
Linking the guest is Link a virtual machine to its host. Start and shut down on the host's own guest list, including a guest that is not linked yet, are Start or shut down a guest from the host. A check that the guest is running is Check that a virtual machine is running. The console window itself is not part of this guide.