I'm having some issues recently with my xFi router and HomeKit accessories, it looks like multicast traffic isn't flowing well and thus HomeKit can't see all of my accessories. HomeKit uses Bonjour which is multicast messages containing some extra info, if these don't flow to all devices then the HomeKit infrastructure doesn't work.
Everything was working fine last week, but recently stopped. I can use an app called "Discovery" on Mac to see what devices are broadcasting successfully and only ethernet devices (accessory bridges) seem to work.
I've tried rebooting the router many times, and tried disabling "Prefer Private Connection" at 10.0.0.1, which I'm not sure is related or not. I'm using the new white xFi gigabit modem + router, with no other network devices except an ethernet switch.