I got this error when attempted to start the KVM VPS from within Virtualizor:

Unable to read from monitor: Connection reset by peer

this was in the logfile /var/log/libvirt/qemu/v1004.log

qemu-kvm: -device Intel,netdev=hostnet0,id=net0,mac=00:16:3e:*:*:*,b us=pci.0,addr=0x3: Parameter 'driver' expects a driver name
What worked was to change VPS configuration by selecting different plan and then start VPS.

Other advice is to run:
virsh managedsave-remove mymachinenamehere