[libvirt-users] Problem with USB pass through after switching to Xenial from Trusty

I use a virtual machine for a scanner I have for which the vendor never updated their driver. I have accessed it for years using a pass through: <hostdev mode='subsystem' type='usb' managed='yes'> <source> <vendor id='0x055f'/> <product id='0x040b'/> </source> </hostdev> I brought this over from the old config and although the machine boots as if it sees it, all I get with an lsusb it that the VM's usb hub exists. The scanner is showing on the host machine. I tried deleting the device and remapping it in virt-manager and then restarting the vm. No joy. So what has changed, or was there something I may have had to do 4 years ago to set this up that I have long forgotten? Perhaps some hack in udev on the host? I really need access to this scanner... like 4 hours ago!